Copyright
Copyright (C) 1986 - 1993, 1998 Thomas Williams, Colin Kelley
Permission to use, copy, and distribute this software and its
documentation for any purpose with or without fee is hereby granted,
provided that the above copyright notice appear in all copies and
that both that copyright notice and this permission notice appear
in supporting documentation.
Permission to modify the software is granted, but not the right to
distribute the complete modified source code. Modifications are to
be distributed as patches to the released version. Permission to
distribute binaries produced by compiling modified sources is granted,
provided you
1. distribute the corresponding source modifications from the
released version in the form of a patch file along with the binaries,
2. add special version identification to distinguish your version
in addition to the base release version number,
3. provide your name and address as the primary contact for the
support of your modified version, and
4. retain our contact information in regard to use of the base
software.
Permission to distribute the released version of the source code along
with corresponding source modifications in the form of a patch file is
granted with same provisions 2 through 4 for binary distributions.
This software is provided "as is" without express or implied warranty
to the extent permitted by applicable law.
AUTHORS
Original Software:
Thomas Williams, Colin Kelley.
Gnuplot 2.0 additions:
Russell Lang, Dave Kotz, John Campbell.
Gnuplot 3.0 additions:
Gershon Elber and many others.
Introduction
gnuplot is a command-driven interactive function and data plotting program.
It is case sensitive (commands and function names written in lowercase are
not the same as those written in CAPS). All command names may be abbreviated
as long as the abbreviation is not ambiguous. Any number of commands may
appear on a line (with the exception that load or call must be the final
command), separated by semicolons (;). Strings are indicated with quotes.
They may be either single or double quotation marks, e.g.,
load "filename"
cd 'dir'
although there are some subtle differences (see syntax for more details).
Any command-line arguments are assumed to be names of files containing
gnuplot commands, with the exception of standard X11 arguments, which are
processed first. Each file is loaded with the load command, in the order
specified. gnuplot exits after the last file is processed. When no load
files are named, gnuplot enters into an interactive mode. The special
filename "-" is used to denote standard input. See "help batch/interactive"
for more details.
Many gnuplot commands have multiple options. These options must appear in
the proper order, although unwanted ones may be omitted in most cases. Thus
if the entire command is "command a b c", then "command a c" will probably
work, but "command c a" will fail.
Commands may extend over several input lines by ending each line but the last
with a backslash (\). The backslash must be the _last_ character on each
line. The effect is as if the backslash and newline were not there. That
is, no white space is implied, nor is a comment terminated. Therefore,
commenting out a continued line comments out the entire command (see
comment). But note that if an error occurs somewhere on a multi-line
command, the parser may not be able to locate precisely where the error is
and in that case will not necessarily point to the correct line.
In this document, curly braces ({}) denote optional arguments and a vertical
bar (|) separates mutually exclusive choices. gnuplot keywords or help
topics are indicated by backquotes or boldface (where available). Angle
brackets (<>) are used to mark replaceable tokens. In many cases, a default
value of the token will be taken for optional arguments if the token is
omitted, but these cases are not always denoted with braces around the angle
brackets.
For on-line help on any topic, type help followed by the name of the topic
or just help or ? to get a menu of available topics.
The new gnuplot user should begin by reading about plotting (if on-line,
type help plotting).
Simple Plots Demo
Seeking-assistance
There is a mailing list for gnuplot users. Note, however, that the
newsgroup
comp.graphics.apps.gnuplot
is identical to the mailing list (they both carry the same set of messages).
We prefer that you read the messages through the newsgroup rather than
subscribing to the mailing list. Administrative requests should be sent to
majordomo@dartmouth.edu
Send a message with the body (not the subject) consisting of the single word
"help" (without the quotes) for more details.
The address for mailing to list members is:
info-gnuplot@dartmouth.edu
Bug reports and code contributions should be mailed to:
bug-gnuplot@dartmouth.edu
The list of those interested in beta-test versions is:
info-gnuplot-beta@dartmouth.edu
There is also a World Wide Web page with up-to-date information, including
known bugs:
http://www.cs.dartmouth.edu/gnuplot_info.html
Before seeking help, please check the
FAQ (Frequently Asked Questions) list.
If you do not have a copy of the FAQ, you may request a copy by email from
the Majordomo address above, ftp a copy from
ftp://ftp.ucc.ie/pub/gnuplot/faq,
ftp://ftp.gnuplot.vt.edu/pub/gnuplot/faq,
or see the WWW gnuplot page.
When posting a question, please include full details of the version of
gnuplot, the machine, and operating system you are using. A _small_ script
demonstrating the problem may be useful. Function plots are preferable to
datafile plots. If email-ing to info-gnuplot, please state whether or not
you are subscribed to the list, so that users who use news will know to email
a reply to you. There is a form for such postings on the WWW site.
What's New in version 3.7
Gnuplot version 3.7 contains many new features. This section gives a partial
list and links to the new items in no particular order.
1. fit f(x) 'file' via uses the Marquardt-Levenberg method to fit data.
(This is only slightly different from the gnufit patch available for 3.5.)
2. Greatly expanded using command. See plot using.
3. set timefmt allows for the use of dates as input and output for time
series plots. See Time/Date data and
timedat.dem.
4. Multiline labels and font selection in some drivers.
5. Minor (unlabeled) tics. See set mxtics.
6. key options for moving the key box in the page (and even outside of the
plot), putting a title on it and a box around it, and more. See set key.
7. Multiplots on a single logical page with set multiplot.
8. Enhanced postscript driver with super/subscripts and font changes.
(This was a separate driver (enhpost) that was available as a patch for
3.5.)
9. Second axes: use the top and right axes independently of the bottom and
left, both for plotting and labels. See plot.
10. Special datafile names '-' and "". See plot special-filenames.
11. Additional coordinate systems for labels and arrows. See coordinates.
12. set size can try to plot with a specified aspect ratio.
13. set missing now treats missing data correctly.
14. The call command: load with arguments.
15. More flexible range commands with reverse, writeback and 'restore'
keywords.
16. set encoding for multi-lingual encoding.
17. New x11 driver with persistent and multiple windows.
18. New plotting styles: xerrorbars, histeps, financebars and more.
See set style.
19. New tic label formats, including "%l %L" which uses the mantissa and
exponents to a given base for labels. See set format.
20. New drivers, including cgm for inclusion into MS-Office applications
and gif for serving plots to the WEB.
21. Smoothing and spline-fitting options for plot. See plot smooth.
22. set margin and set origin give much better control over where a
graph appears on the page.
23. set border now controls each border individually.
24. The new commands if and reread allow command loops.
25. Point styles and sizes, line types and widths can be specified on the
plot command. Line types and widths can also be specified for grids,
borders, tics and arrows. See plot with. Furthermore these types may be
combined and stored for further use. See set linestyle.
26. Text (labels, tic labels, and the time stamp) can be written vertically
by those terminals capable of doing so.
Command-line-editing
Command-line editing is supported by the Unix, Atari, VMS, MS-DOS and OS/2
versions of gnuplot. Also, a history mechanism allows previous commands to
be edited and re-executed. After the command line has been edited, a newline
or carriage return will enter the entire line without regard to where the
cursor is positioned.
(The readline function in gnuplot is not the same as the readline used in
GNU Bash and GNU Emacs. If the GNU version is desired, it may be selected
instead of the gnuplot version at compile time.)
The editing commands are as follows:
Line-editing:
^B moves back a single character.
^F moves forward a single character.
^A moves to the beginning of the line.
^E moves to the end of the line.
^H and DEL delete the previous character.
^D deletes the current character.
^K deletes from current position to the end of line.
^L,^R redraws line in case it gets trashed.
^U deletes the entire line.
^W deletes the last word.
History:
^P moves back through history.
^N moves forward through history.
On the IBM PC, the use of a TSR program such as DOSEDIT or CED may be desired
for line editing. The default makefile assumes that this is the case; by
default gnuplot will be compiled with no line-editing capability. If you
want to use gnuplot's line editing, set READLINE in the makefile and add
readline.obj to the link file. The following arrow keys may be used on the
IBM PC and Atari versions if readline is used:
Left Arrow - same as ^B.
Right Arrow - same as ^F.
Ctrl Left Arrow - same as ^A.
Ctrl Right Arrow - same as ^E.
Up Arrow - same as ^P.
Down Arrow - same as ^N.
The Atari version of readline defines some additional key aliases:
Undo - same as ^L.
Home - same as ^A.
Ctrl Home - same as ^E.
Esc - same as ^U.
Help - help plus return.
Ctrl Help - help .
Coordinates
The commands set arrow, set key, and set label allow you to draw
something at an arbitrary position on the graph. This position is specified
by the syntax:
{<system>} <x>, {<system>} <y> {,{<system>} <z>}
Each <system> can either be first, second, graph or screen.
first places the x, y, or z coordinate in the system defined by the left
and bottom axes; second places it in the system defined by the second axes
(top and right); graph specifies the area within the axes---0,0 is bottom
left and 1,1 is top right (for splot, 0,0,0 is bottom left of plotting area;
use negative z to get to the base---see set ticslevel); and screen
specifies the screen area (the entire area---not just the portion selected by
set size), with 0,0 at bottom left and 1,1 at top right.
If the coordinate system for x is not specified, first is used. If the
system for y is not specified, the one used for x is adopted.
If one (or more) axis is timeseries, the appropriate coordinate should
be given as a quoted time string according to the timefmt format string.
See set xdata and set timefmt. gnuplot will also accept an integer
expression, which will be interpreted as seconds from 1 January 2000.
Environment
A number of shell environment variables are understood by gnuplot. None of
these are required, but may be useful.
If GNUTERM is defined, it is used as the name of the terminal type to be
used. This overrides any terminal type sensed by gnuplot on start-up, but
is itself overridden by the .gnuplot (or equivalent) start-up file (see
start-up) and, of course, by later explicit changes.
On Unix, AmigaOS, AtariTOS, MS-DOS and OS/2, GNUHELP may be defined to be the
pathname of the HELP file (gnuplot.gih).
On VMS, the logical name GNUPLOT$HELP should be defined as the name of the
help library for gnuplot. The gnuplot help can be put inside any system
help library, allowing access to help from both within and outside gnuplot
if desired.
On Unix, HOME is used as the name of a directory to search for a .gnuplot
file if none is found in the current directory. On AmigaOS, AtariTOS,
MS-DOS and OS/2, gnuplot is used. On VMS, SYS$LOGIN: is used. See help
start-up.
On Unix, PAGER is used as an output filter for help messages.
On Unix, AtariTOS and AmigaOS, SHELL is used for the shell command. On
MS-DOS and OS/2, COMSPEC is used for the shell command.
On MS-DOS, if the BGI or Watcom interface is used, PCTRM is used to tell
the maximum resolution supported by your monitor by setting it to
S<max. horizontal resolution>. E.g. if your monitor's maximum resolution is
800x600, then use:
set PCTRM=S800
If PCTRM is not set, standard VGA is used.
FIT_SCRIPT may be used to specify a gnuplot command to be executed when a
fit is interrupted---see fit. FIT_LOG specifies the filename of the
logfile maintained by fit.
Expressions
In general, any mathematical expression accepted by C, FORTRAN, Pascal, or
BASIC is valid. The precedence of these operators is determined by the
specifications of the C programming language. White space (spaces and tabs)
is ignored inside expressions.
Complex constants are expressed as {<real>,<imag>}, where <real> and <imag>
must be numerical constants. For example, {3,2} represents 3 + 2i; {0,1}
represents 'i' itself. The curly braces are explicitly required here.
Note that gnuplot uses both "real" and "integer" arithmetic, like FORTRAN and
C. Integers are entered as "1", "-10", etc; reals as "1.0", "-10.0", "1e1",
3.5e-1, etc. The most important difference between the two forms is in
division: division of integers truncates: 5/2 = 2; division of reals does
not: 5.0/2.0 = 2.5. In mixed expressions, integers are "promoted" to reals
before evaluation: 5/2e0 = 2.5. The result of division of a negative integer
by a positive one may vary among compilers. Try a test like "print -5/2" to
determine if your system chooses -2 or -3 as the answer.
The integer expression "1/0" may be used to generate an "undefined" flag,
which causes a point to ignored; the ternary operator gives an example.
The real and imaginary parts of complex expressions are always real, whatever
the form in which they are entered: in {3,2} the "3" and "2" are reals, not
integers.
Functions
Operators
User-defined
Ternary
There is a single ternary operator:
Symbol Example Explanation
?: a?b:c ternary operation
The ternary operator behaves as it does in C. The first argument (a), which
must be an integer, is evaluated. If it is true (non-zero), the second
argument (b) is evaluated and returned; otherwise the third argument (c) is
evaluated and returned.
The ternary operator is very useful both in constructing piecewise functions
and in plotting points only when certain conditions are met.
Examples:
Plot a function that is to equal sin(x) for 0 <= x < 1, 1/x for 1 <= x < 2,
and undefined elsewhere:
f(x) = 0<=x && x<1 ? sin(x) : 1<=x && x<2 ? 1/x : 1/0
plot f(x)
Note that gnuplot quietly ignores undefined values, so the final branch of
the function (1/0) will produce no plottable points. Note also that f(x)
will be plotted as a continuous function across the discontinuity if a line
style is used. To plot it discontinuously, create separate functions for the
two pieces. (Parametric functions are also useful for this purpose.)
For data in a file, plot the average of the data in columns 2 and 3 against
the datum in column 1, but only if the datum in column 4 is non-negative:
plot 'file' using 1:( $4<0 ? 1/0 : ($2+$3)/2 )
Please see plot data-file using for an explanation of the using syntax.
User-defined
New user-defined variables and functions of one through five variables may
be declared and used anywhere, including on the plot command itself.
User-defined function syntax:
<func-name>( <dummy1> {,<dummy2>} ... {,<dummy5>} ) = <expression>
where <expression> is defined in terms of <dummy1> through <dummy5>.
User-defined variable syntax:
<variable-name> = <constant-expression>
Examples:
w = 2
q = floor(tan(pi/2 - 0.1))
f(x) = sin(w*x)
sinc(x) = sin(pi*x)/(pi*x)
delta(t) = (t == 0)
ramp(t) = (t > 0) ? t : 0
min(a,b) = (a < b) ? a : b
comb(n,k) = n!/(k!*(n-k)!)
len3d(x,y,z) = sqrt(x*x+y*y+z*z)
plot f(x) = sin(x*a), a = 0.2, f(x), a = 0.4, f(x)
Note that the variable pi is already defined. But it is in no way magic;
you may redefine it to be whatever you like.
Valid names are the same as in most programming languages: they must begin
with a letter, but subsequent characters may be letters, digits, "$", or "_".
Note, however, that the fit mechanism uses several variables with names
that begin "FIT_". It is safest to avoid using such names. "FIT_LIMIT",
however, is one that you may wish to redefine. See the documentation
on fit for details.
See show functions, show variables, and fit.
Glossary
Throughout this document an attempt has been made to maintain consistency of
nomenclature. This cannot be wholly successful because as gnuplot has
evolved over time, certain command and keyword names have been adopted that
preclude such perfection. This section contains explanations of the way
some of these terms are used.
A "page" or "screen" is the entire area addressable by gnuplot. On a
monitor, it is the full screen; on a plotter, it is a single sheet of paper.
A screen may contain one or more "plots". A plot is defined by an abscissa
and an ordinate, although these need not actually appear on it, as well as
the margins and any text written therein.
A plot contains one "graph". A graph is defined by an abscissa and an
ordinate, although these need not actually appear on it.
A graph may contain one or more "lines". A line is a single function or
data set. "Line" is also a plotting style. The word will also be used in
sense "a line of text". Presumably the context will remove any ambiguity.
The lines on a graph may have individual names. These may be listed
together with a sample of the plotting style used to represent them in
the "key", sometimes also called the "legend".
The word "title" occurs with multiple meanings in gnuplot. In this
document, it will always be preceded by the adjective "plot", "line", or
"key" to differentiate among them.
A graph may have up to four labelled axes. Various commands have the name of
an axis built into their names, such as set xlabel. Other commands have
one or more axis names as options, such as set logscale xy. The names of
the four axes for these usages are "x" for the axis along the bottom border
of the plot, "y" for the left border, "x2" for the top border, and "y2" for
the right border. "z" also occurs in commands used with 3-d plotting.
When discussing data files, the term "record" will be resurrected and used
to denote a single line of text in the file, that is, the characters between
newline or end-of-record characters. A "point" is the datum extracted from
a single record. A "datablock" is a set of points from consecutive records,
delimited by blank records. A line, when referred to in the context of a
data file, is a subset of a datablock.
Syntax
The general rules of syntax and punctuation in gnuplot are that keywords
and options are order-dependent. Options and any accompanying parameters are
separated by spaces whereas lists and coordinates are separated by commas.
Ranges are separated by colons and enclosed in brackets [], text and file
names are enclosed in quotes, and a few miscellaneous things are enclosed
in parentheses. Braces {} are used for a few special purposes.
Commas are used to separate coordinates on the set commands arrow,
key, and label; the list of variables being fitted (the list after the
via keyword on the fit command); lists of discrete contours or the loop
parameters which specify them on the set cntrparam command; the arguments
of the set commands dgrid3d, dummy, isosamples, offsets, origin,
samples, size, time, and view; lists of tics or the loop parameters
which specify them; the offsets for titles and axis labels; parametric
functions to be used to calculate the x, y, and z coordinates on the plot,
replot and splot commands; and the complete sets of keywords specifying
individual plots (data sets or functions) on the plot, replot and splot
commands.
Parentheses are used to delimit sets of explicit tics (as opposed to loop
parameters) and to indicate computations in the using filter of the fit,
plot, replot and splot commands.
(Parentheses and commas are also used as usual in function notation.)
Brackets are used to delimit ranges, whether they are given on set, plot
or splot commands.
Colons are used to separate extrema in range specifications (whether they
are given on set, plot or splot commands) and to separate entries in
the using filter of the plot, replot, splot and fit commands.
Semicolons are used to separate commands given on a single command line.
Braces are used in text to be specially processed by some terminals, like
postscript. They are also used to denote complex numbers: {3,2} = 3 + 2i.
Text may be enclosed in single- or double-quotes. Backslash processing of
sequences like \n (newline) and \345 (octal character code) is performed for
double-quoted strings, but not for single-quoted strings.
The justification is the same for each line of a multi-line string. Thus the
center-justified string
"This is the first line of text.\nThis is the second line."
will produce
This is the first line of text.
This is the second line.
but
'This is the first line of text.\nThis is the second line.'
will produce
This is the first line of text.\nThis is the second line.
Filenames may be entered with either single- or double-quotes. In this
manual the command examples generally single-quote filenames and double-quote
other string tokens for clarity.
At present you should not embed \n inside {} when using the enhanced option
of the postscript terminal.
The EEPIC, Imagen, Uniplex, LaTeX, and TPIC drivers allow a newline to be
specified by \\ in a single-quoted string or \\\\ in a double-quoted string.
Back-quotes are used to enclose system commands for substitution.
Time/Date data
gnuplot supports the use of time and/or date information as input data.
This feature is activated by the commands set xdata time, set ydata time,
etc.
Internally all times and dates are converted to the number of seconds from
the year 2000. The command set timefmt defines the format for all inputs:
data files, ranges, tics, label positions---in short, anything that accepts a
data value must receive it in this format. Since only one input format can
be in force at a given time, all time/date quantities being input at the same
time must be presented in the same format. Thus if both x and y data in a
file are time/date, they must be in the same format.
The conversion to and from seconds assumes Universal Time (which is the same
as Greenwich Standard Time). There is no provision for changing the time
zone or for daylight savings. If all your data refer to the same time zone
(and are all either daylight or standard) you don't need to worry about these
things. But if the absolute time is crucial for your application, you'll
need to convert to UT yourself.
Commands like show xrange will re-interpret the integer according to
timefmt. If you change timefmt, and then show the quantity again, it
will be displayed in the new timefmt. For that matter, if you give the
deactivation command (like set xdata), the quantity will be shown in its
numerical form.
The command set format defines the format that will be used for tic labels,
whether or not the specified axis is time/date.
If time/date information is to be plotted from a file, the using option
_must_ be used on the plot or splot command. These commands simply use
white space to separate columns, but white space may be embedded within the
time/date string. If you use tabs as a separator, some trial-and-error may
be necessary to discover how your system treats them.
The following example demonstrates time/date plotting.
Suppose the file "data" contains records like
03/21/95 10:00 6.02e23
This file can be plotted by
set xdata time
set timefmt "%m/%d/%y"
set xrange ["03/21/95":"03/22/95"]
set format x "%m/%d"
set timefmt "%m/%d/%y %H:%M"
plot "data" using 1:3
which will produce xtic labels that look like "03/21".
See the descriptions of each command for more details.
call
The call command is identical to the load command with one exception: you
can have up to ten additional parameters to the command (delimited according
to the standard parser rules) which can be substituted into the lines read
from the file. As each line is read from the called input file, it is
scanned for the sequence $ (dollar-sign) followed by a digit (0--9). If
found, the sequence is replaced by the corresponding parameter from the
call command line. If the parameter was specified as a string in the
call line, it is substituted without its enclosing quotes. $ followed by
any character other than a digit will be that character. E.g. use $$ to
get a single $. Providing more than ten parameters on the call command
line will cause an error. A parameter that was not provided substitutes as
nothing. Files being called may themselves contain call or load
commands.
The call command _must_ be the last command on a multi-command line.
Syntax:
call "<input-file>" <parameter-0> <parm-1> ... <parm-9>
The name of the input file must be enclosed in quotes, and it is recommended
that parameters are similarly enclosed in quotes (future versions of gnuplot
may treat quoted and unquoted arguments differently).
Example:
If the file 'calltest.gp' contains the line:
print "p0=$0 p1=$1 p2=$2 p3=$3 p4=$4 p5=$5 p6=$6 p7=x$7x"
entering the command:
call 'calltest.gp' "abcd" 1.2 + "'quoted'" -- "$2"
will display:
p0=abcd p1=1.2 p2=+ p3='quoted' p4=- p5=- p6=$2 p7=xx
NOTE: there is a clash in syntax with the datafile using callback
operator. Use $$n or column(n) to access column n from a datafile inside
a called datafile plot.
fit
The fit command can fit a user-defined function to a set of data points
(x,y) or (x,y,z), using an implementation of the nonlinear least-squares
(NLLS) Marquardt-Levenberg algorithm. Any user-defined variable occurring in
the function body may serve as a fit parameter, but the return type of the
function must be real.
Syntax:
fit {[xrange] {[yrange]}} <function> '<datafile>'
{datafile-modifiers}
via '<parameter file>' | <var1>{,<var2>,...}
Ranges may be specified to temporarily limit the data which is to be fitted;
any out-of-range data points are ignored. The syntax is
[{dummy_variable=}{<min>}{:<max>}],
analogous to plot; see plot ranges.
<function> is any valid gnuplot expression, although it is usual to use a
previously user-defined function of the form f(x) or f(x,y).
<datafile> is treated as in the plot command. All the plot datafile
modifiers (using, every,...) except smooth are applicable to fit.
See plot datafile.
The default data formats for fitting functions with a single independent
variable, y=f(x), are {x:}y or x:y:s; those formats can be changed with
the datafile using qualifier. The third item, (a column number or an
expression), if present, is interpreted as the standard deviation of the
corresponding y value and is used to compute a weight for the datum, 1/s**2.
Otherwise, all data points are weighted equally, with a weight of one.
To fit a function with two independent variables, z=f(x,y), the required
format is using with four items, x:y:z:s. The complete format must be
given---no default columns are assumed for a missing token. Weights for
each data point are evaluated from 's' as above. If error estimates are
not available, a constant value can be specified as a constant expression
(see plot datafile using), e.g., using 1:2:3:(1).
Multiple datasets may be simultaneously fit with functions of one
independent variable by making y a 'pseudo-variable', e.g., the dataline
number, and fitting as two independent variables. See fit multibranch.
The via qualifier specifies which parameters are to be adjusted, either
directly, or by referencing a parameter file.
Examples:
f(x) = a*x**2 + b*x + c
g(x,y) = a*x**2 + b*y**2 + c*x*y
FIT_LIMIT = 1e-6
fit f(x) 'measured.dat' via 'start.par'
fit f(x) 'measured.dat' using 3:($7-5) via 'start.par'
fit f(x) './data/trash.dat' using 1:2:3 via a, b, c
fit g(x,y) 'surface.dat' using 1:2:3:(1) via a, b, c
After each iteration step, detailed information about the current state
of the fit is written to the display. The same information about the
initial and final states is written to a log file, "fit.log". This file
is always appended to, so as to not lose any previous fit history; it
should be deleted or renamed as desired.
The fit may be interrupted by pressing Ctrl-C (any key but Ctrl-C under
MSDOS and Atari Multitasking Systems). After the current iteration
completes, you have the option to (1) stop the fit and accept the current
parameter values, (2) continue the fit, (3) execute a gnuplot command
as specified by the environment variable FIT_SCRIPT. The default for
FIT_SCRIPT is replot, so if you had previously plotted both the data
and the fitting function in one graph, you can display the current state
of the fit.
Once fit has finished, the update command may be used to store final
values in a file for subsequent use as a parameter file. See update
for details.
adjustable parameters
beginner's guide
error estimates
fit controlling
multi-branch
starting values
tips
beginner's guide
fit is used to find a set of parameters that 'best' fits your data to your
user-defined function. The fit is judged on the basis of the the sum of the
squared differences or 'residuals' (SSR) between the input data points and
the function values, evaluated at the same places. This quantity is often
called 'chisquare' (i.e., the Greek letter chi, to the power of 2). The
algorithm attempts to minimize SSR, or more precisely, WSSR, as the residuals
are 'weighted' by the input data errors (or 1.0) before being squared; see
fit error_estimates for details.
That's why it is called 'least-squares fitting'. Let's look at an example
to see what is meant by 'non-linear', but first we had better go over some
terms. Here it is convenient to use z as the dependent variable for
user-defined functions of either one independent variable, z=f(x), or two
independent variables, z=f(x,y). A parameter is a user-defined variable
that fit will adjust, i.e., an unknown quantity in the function
declaration. Linearity/non-linearity refers to the relationship of the
dependent variable, z, to the parameters which fit is adjusting, not of
z to the independent variables, x and/or y. (To be technical, the
second {and higher} derivatives of the fitting function with respect to
the parameters are zero for a linear least-squares problem).
For linear least-squares (LLS), the user-defined function will be a sum of
simple functions, not involving any parameters, each multiplied by one
parameter. NLLS handles more complicated functions in which parameters can
be used in a large number of ways. An example that illustrates the
difference between linear and nonlinear least-squares is the Fourier series.
One member may be written as
z=a*sin(c*x) + b*cos(c*x).
If a and b are the unknown parameters and c is constant, then estimating
values of the parameters is a linear least-squares problem. However, if
c is an unknown parameter, the problem is nonlinear.
In the linear case, parameter values can be determined by comparatively
simple linear algebra, in one direct step. However LLS is a special case
which is also solved along with more general NLLS problems by the iterative
procedure that gnuplot uses. fit attempts to find the minimum by doing
a search. Each step (iteration) calculates WSSR with a new set of parameter
values. The Marquardt-Levenberg algorithm selects the parameter values for
the next iteration. The process continues until a preset criterium is met,
either (1) the fit has "converged" (the relative change in WSSR is less than
FIT_LIMIT), or (2) it reaches a preset iteration count limit, FIT_MAXITER
(see fit control variables). The fit may also be interrupted
and subsequently halted from the keyboard (see fit).
Often the function to be fitted will be based on a model (or theory) that
attempts to describe or predict the behaviour of the data. Then fit can
be used to find values for the free parameters of the model, to determine
how well the data fits the model, and to estimate an error range for each
parameter. See fit error_estimates.
Alternatively, in curve-fitting, functions are selected independent of
a model (on the basis of experience as to which are likely to describe
the trend of the data with the desired resolution and a minimum number
of parameters*functions.) The fit solution then provides an analytic
representation of the curve.
However, if all you really want is a smooth curve through your data points,
the smooth option to plot may be what you've been looking for rather
than fit.
statistical overview
The theory of non-linear least-squares (NLLS) is generally described in terms
of a normal distribution of errors, that is, the input data is assumed to be
a sample from a population having a given mean and a Gaussian (normal)
distribution about the mean with a given standard deviation. For a sample of
sufficiently large size, and knowing the population standard deviation, one
can use the statistics of the chisquare distribution to describe a "goodness
of fit" by looking at the variable often called "chisquare". Here, it is
sufficient to say that a reduced chisquare (chisquare/degrees of freedom,
where degrees of freedom is the number of datapoints less the number of
parameters being fitted) of 1.0 is an indication that the weighted sum of
squared deviations between the fitted function and the data points is the
same as that expected for a random sample from a population characterized by
the function with the current value of the parameters and the given standard
deviations.
If the standard deviation for the population is not constant, as in counting
statistics where variance = counts, then each point should be individually
weighted when comparing the observed sum of deviations and the expected sum
of deviations.
At the conclusion fit reports 'stdfit', the standard deviation of the fit,
which is the rms of the residuals, and the variance of the residuals, also
called 'reduced chisquare' when the data points are weighted. The number of
degrees of freedom (the number of data points minus the number of fitted
parameters) is used in these estimates because the parameters used in
calculating the residuals of the datapoints were obtained from the same data.
To estimate confidence levels for the parameters, one can use the minimum
chisquare obtained from the fit and chisquare statistics to determine the
value of chisquare corresponding to the desired confidence level, but
considerably more calculation is required to determine the combinations of
parameters which produce such values.
Rather than determine confidence intervals, fit reports parameter error
estimates which are readily obtained from the variance-covariance matrix
after the final iteration. By convention, these estimates are called
"standard errors" or "asymptotic standard errors", since they are calculated
in the same way as the standard errors (standard deviation of each parameter)
of a linear least-squares problem, even though the statistical conditions for
designating the quantity calculated to be a standard deviation are not
generally valid for the NLLS problem. The asymptotic standard errors are
generally over-optimistic and should not be used for determining confidence
levels, but are useful for qualitative purposes.
The final solution also produces a correlation matrix, which gives an
indication of the correlation of parameters in the region of the solution;
if one parameter is changed, increasing chisquare, does changing another
compensate? The main diagonal elements, autocorrelation, are all 1; if
all parameters were independent, all other elements would be nearly 0. Two
variables which completely compensate each other would have an off-diagonal
element of unit magnitude, with a sign depending on whether the relation is
proportional or inversely proportional. The smaller the magnitudes of the
off-diagonal elements, the closer the estimates of the standard deviation
of each parameter would be to the asymptotic standard error.
practical guidelines
If you have a basis for assigning weights to each data point, doing so lets
you make use of additional knowledge about your measurements, e.g., take into
account that some points may be more reliable than others. That may affect
the final values of the parameters.
Weighting the data provides a basis for interpreting the additional fit
output after the last iteration. Even if you weight each point equally,
estimating an average standard deviation rather than using a weight of 1
makes WSSR a dimensionless variable, as chisquare is by definition.
Each fit iteration will display information which can be used to evaluate
the progress of the fit. (An '*' indicates that it did not find a smaller
WSSR and is trying again.) The 'sum of squares of residuals', also called
'chisquare', is the WSSR between the data and your fitted function; fit
has minimized that. At this stage, with weighted data, chisquare is expected
to approach the number of degrees of freedom (data points minus parameters).
The WSSR can be used to calculate the reduced chisquare (WSSR/ndf) or stdfit,
the standard deviation of the fit, sqrt(WSSR/ndf). Both of these are
reported for the final WSSR.
If the data are unweighted, stdfit is the rms value of the deviation of the
data from the fitted function, in user units.
If you supplied valid data errors, the number of data points is large enough,
and the model is correct, the reduced chisquare should be about unity. (For
details, look up the 'chi-squared distribution' in your favourite statistics
reference.) If so, there are additional tests, beyond the scope of this
overview, for determining how well the model fits the data.
A reduced chisquare much larger than 1.0 may be due to incorrect data error
estimates, data errors not normally distributed, systematic measurement
errors, 'outliers', or an incorrect model function. A plot of the residuals,
e.g., plot 'datafile' using 1:($2-f($1)), may help to show any systematic
trends. Plotting both the data points and the function may help to suggest
another model.
Similarly, a reduced chisquare less than 1.0 indicates WSSR is less than that
expected for a random sample from the function with normally distributed
errors. The data error estimates may be too large, the statistical
assumptions may not be justified, or the model function may be too general,
fitting fluctuations in a particular sample in addition to the underlying
trends. In the latter case, a simpler function may be more appropriate.
You'll have to get used to both fit and the kind of problems you apply it
to before you can relate the standard errors to some more practical estimates
of parameter uncertainties or evaluate the significance of the correlation
matrix.
Note that fit, in common with most NLLS implementations, minimizes the
weighted sum of squared distances (y-f(x))**2. It does not provide any means
to account for "errors" in the values of x, only in y. Also, any "outliers"
(data points outside the normal distribution of the model) will have an
exaggerated effect on the solution.
control variables
The default epsilon limit (1e-5) may be changed by declaring a value for
FIT_LIMIT
When the sum of squared residuals changes between two iteration steps by
a factor less than this number (epsilon), the fit is considered to have
'converged'.
The maximum number of iterations may be limited by declaring a value for
FIT_MAXITER
A value of 0 (or not defining it at all) means that there is no limit.
If you need even more control about the algorithm, and know the
Marquardt-Levenberg algorithm well, there are some more variables to
influence it. The startup value of lambda is normally calculated
automatically from the ML-matrix, but if you want to, you may provide
your own one with
FIT_START_LAMBDA
Specifying FIT_START_LAMBDA as zero or less will re-enable the automatic
selection. The variable
FIT_LAMBDA_FACTOR
gives the factor by which lambda is increased or decreased whenever
the chi-squared target function increased or decreased significantly.
Setting FIT_LAMBDA_FACTOR to zero re-enables the default factor of
10.0.
Oher variables with the FIT_ prefix may be added to fit, so it is safer
not to use that prefix for user-defined variables.
The variables FIT_SKIP and FIT_INDEX were used by earlier releases of
gnuplot with a 'fit' patch called gnufit and are no longer available.
The datafile every modifier provides the functionality of FIT_SKIP.
FIT_INDEX was used for multi-branch fitting, but multi-branch fitting of
one independent variable is now done as a pseudo-3D fit in which the
second independent variable and using are used to specify the branch.
See fit multi-branch.
multi-branch
In multi-branch fitting, multiple data sets can be simultaneously fit with
functions of one independent variable having common parameters by minimizing
the total WSSR. The function and parameters (branch) for each data set are
selected by using a 'pseudo-variable', e.g., either the dataline number (a
'column' index of -1) or the datafile index (-2), as the second independent
variable.
Example: Given two exponential decays of the form, z=f(x), each describing
a different data set but having a common decay time, estimate the values of
the parameters. If the datafile has the format x:z:s, then
f(x,y) = (y==0) ? a*exp(-x/tau) : b*exp(-x/tau)
fit f(x,y) 'datafile' using 1:-1:2:3 via a, b, tau
For a more complicated example, see the file "hexa.fnc" used by the
"fit.dem" demo.
Appropriate weighting may be required since unit weights may cause one
branch to predominate if there is a difference in the scale of the dependent
variable. Fitting each branch separately, using the multi-branch solution
as initial values, may give an indication as to the relative effect of each
branch on the joint solution.
starting values
Nonlinear fitting is not guaranteed to converge to the global optimum (the
solution with the smallest sum of squared residuals, SSR), and can get stuck
at a local minimum. The routine has no way to determine that; it is up to
you to judge whether this has happened.
fit may, and often will get "lost" if started far from a solution, where
SSR is large and changing slowly as the parameters are varied, or it may
reach a numerically unstable region (e.g., too large a number causing a
floating point overflow) which results in an "undefined value" message
or gnuplot halting.
To improve the chances of finding the global optimum, you should set the
starting values at least roughly in the vicinity of the solution, e.g.,
within an order of magnitude, if possible. The closer your starting values
are to the solution, the less chance of stopping at another minimum. One way
to find starting values is to plot data and the fitting function on the same
graph and change parameter values and replot until reasonable similarity
is reached. The same plot is also useful to check whether the fit stopped at
a minimum with a poor fit.
Of course, a reasonably good fit is not proof there is not a "better" fit (in
either a statistical sense, characterized by an improved goodness-of-fit
criterion, or a physical sense, with a solution more consistent with the
model.) Depending on the problem, it may be desirable to fit with various
sets of starting values, covering a reasonable range for each parameter.
tips
Here are some tips to keep in mind to get the most out of fit. They're not
very organized, so you'll have to read them several times until their essence
has sunk in.
The two forms of the via argument to fit serve two largely distinct
purposes. The via "file" form is best used for (possibly unattended) batch
operation, where you just supply the startup values in a file and can later
use update to copy the results back into another (or the same) parameter
file.
The via var1, var2, ... form is best used interactively, where the command
history mechanism may be used to edit the list of parameters to be fitted or
to supply new startup values for the next try. This is particularly useful
for hard problems, where a direct fit to all parameters at once won't work
without good starting values. To find such, you can iterate several times,
fitting only some of the parameters, until the values are close enough to the
goal that the final fit to all parameters at once will work.
Make sure that there is no mutual dependency among parameters of the function
you are fitting. For example, don't try to fit a*exp(x+b), because
a*exp(x+b)=a*exp(b)*exp(x). Instead, fit either a*exp(x) or exp(x+b).
A technical issue: the parameters must not be too different in magnitude.
The larger the ratio of the largest and the smallest absolute parameter
values, the slower the fit will converge. If the ratio is close to or above
the inverse of the machine floating point precision, it may take next to
forever to converge, or refuse to converge at all. You will have to adapt
your function to avoid this, e.g., replace 'parameter' by '1e9*parameter' in
the function definition, and divide the starting value by 1e9.
If you can write your function as a linear combination of simple functions
weighted by the parameters to be fitted, by all means do so. That helps a
lot, because the problem is no longer nonlinear and should converge with only
a small number of iterations, perhaps just one.
Some prescriptions for analysing data, given in practical experimentation
courses, may have you first fit some functions to your data, perhaps in a
multi-step process of accounting for several aspects of the underlying
theory one by one, and then extract the information you really wanted from
the fitting parameters of those functions. With fit, this may often be
done in one step by writing the model function directly in terms of the
desired parameters. Transforming data can also quite often be avoided,
though sometimes at the cost of a more difficult fit problem. If you think
this contradicts the previous paragraph about simplifying the fit function,
you are correct.
A "singular matrix" message indicates that this implementation of the
Marquardt-Levenberg algorithm can't calculate parameter values for the next
iteration. Try different starting values, writing the function in another
form, or a simpler function.
Finally, a nice quote from the manual of another fitting package (fudgit),
that kind of summarizes all these issues: "Nonlinear fitting is an art!"
plot
plot is the primary command for drawing plots with gnuplot. It creates
plots of functions and data in many, many ways. plot is used to draw 2-d
functions and data; splot draws 2-d projections of 3-d surfaces and data.
plot and splot contain many common features; see splot for differences.
Note specifically that splot's binary and matrix options do not exist
for plot.
Syntax:
plot {<ranges>}
{<function> | {"<datafile>" {datafile-modifiers}}}
{axes <axes>} {<title-spec>} {with <style>}
{, {definitions,} <function> ...}
where either a <function> or the name of a data file enclosed in quotes is
supplied. A function is a mathematical expression or a pair of mathematical
expressions in parametric mode. The expressions may be defined completely or
in part earlier in the stream of gnuplot commands (see user-defined).
It is also possible to define functions and parameters on the plot command
itself. This is done merely by isolating them from other items with commas.
There are four possible sets of axes available; the keyword <axes> is used to
select the axes for which a particular line should be scaled. x1y1 refers
to the axes on the bottom and left; x2y2 to those on the top and right;
x1y2 to those on the bottom and right; and x2y1 to those on the top and
left. Ranges specified on the plot command apply only to the first set of
axes (bottom left).
Examples:
plot sin(x)
plot f(x) = sin(x*a), a = .2, f(x), a = .4, f(x)
plot [t=1:10] [-pi:pi*2] tan(t), \
"data.1" using (tan($2)):($3/$4) smooth csplines \
axes x1y2 notitle with lines 5
data-file
errorbars
parametric
ranges
title
with
data-file
Discrete data contained in a file can be displayed by specifying the name of
the data file (enclosed in single or double quotes) on the plot command line.
Syntax:
plot '<file_name>' {index <index list>}
{every <every list>}
{thru <thru expression>}
{using <using list>}
{smooth <option>}
The modifiers index, every, thru, using, and smooth are discussed
separately. In brief, index selects which data sets in a multi-data-set
file are to be plotted, every specifies which points within a single data
set are to be plotted, using determines how the columns within a single
record are to be interpreted (thru is a special case of using), and
smooth allows for simple interpolation and approximation. ('splot' has a
similar syntax, but does not support the smooth and thru options.)
Data files should contain at least one data point per record (using can
select one data point from the record). Records beginning with # (and
also with ! on VMS) will be treated as comments and ignored. Each data
point represents an (x,y) pair. For plots with error bars (see set style
errorbars), each data point is (x,y,ydelta), (x,y,ylow,yhigh), (x,y,xdelta),
(x,y,xlow,xhigh), or (x,y,xlow,xhigh,ylow,yhigh). In all cases, the numbers
on each record of a data file must be separated by white space (one or more
blanks or tabs), unless a format specifier is provided by the using option.
This white space divides each record into columns.
Data may be written in exponential format with the exponent preceded by the
letter e, E, d, D, q, or Q.
Only one column (the y value) need be provided. If x is omitted, gnuplot
provides integer values starting at 0.
In datafiles, blank records (records with no characters other than blanks and
a newline and/or carriage return) are significant---pairs of blank records
separate indexes (see plot datafile index). Data separated by double
blank records are treated as if they were in separate data files.
Single blank records designate discontinuities in a plot; no line will join
points separated by a blank records (if they are plotted with a line style).
If autoscaling has been enabled (set autoscale), the axes are automatically
extended to include all datapoints, with a whole number of tic marks if tics
are being drawn. This has two consequences: i) For splot, the corner of
the surface may not coincide with the corner of the base. In this case, no
vertical line is drawn. ii) When plotting data with the same x range on a
dual-axis graph, the x coordinates may not coincide if the x2tics are not
being drawn. This is because the x axis has been autoextended to a whole
number of tics, but the x2 axis has not. The following example illustrates
the problem:
reset; plot '-', '-'
1 1
19 19
e
1 1
19 19
e
every
example datafile
index
smooth
special-filenames
thru
using
every
The every keyword allows a periodic sampling of a data set to be plotted.
In the discussion a "point" is a datum defined by a single record in the
file; "block" here will mean the same thing as "datablock" (see glossary).
Syntax:
plot 'file' every {<point_incr>}
{:{<block_incr>}
{:{<start_point>}
{:{<start_block>}
{:{<end_point>}
{:<end_block>}}}}}
The data points to be plotted are selected according to a loop from
<start_point> to <end_point> with increment <point_incr> and the
blocks according to a loop from <start_block> to <end_block> with
increment <block_incr>.
The first datum in each block is numbered '0', as is the first block in the
file.
Note that records containing unplottable information are counted.
Any of the numbers can be omitted; the increments default to unity, the start
values to the first point or block, and the end values to the last point or
block. If every is not specified, all points in all lines are plotted.
Examples:
every :::3::3 # selects just the fourth block ('0' is first)
every :::::9 # selects the first 10 blocks
every 2:2 # selects every other point in every other block
every ::5::15 # selects points 5 through 15 in each block
Simple Plot Demos ,
Non-parametric splot demos , and
Parametric splot demos.
special-filenames
A special filename of '-' specifies that the data are inline; i.e., they
follow the command. Only the data follow the command; plot options like
filters, titles, and line styles remain on the 'plot' command line. This is
similar to << in unix shell script, and $DECK in VMS DCL. The data are
entered as though they are being read from a file, one data point per record.
The letter "e" at the start of the first column terminates data entry. The
using option can be applied to these data---using it to filter them through
a function might make sense, but selecting columns probably doesn't!
'-' is intended for situations where it is useful to have data and commands
together, e.g., when gnuplot is run as a sub-process of some front-end
application. Some of the demos, for example, might use this feature. While
plot options such as index and every are recognized, their use forces
you to enter data that won't be used. For example, while
plot '-' index 0, '-' index 1
2
4
6
10
12
14
e
2
4
6
10
12
14
e
does indeed work,
plot '-', '-'
2
4
6
e
10
12
14
e
is a lot easier to type.
If you use '-' with replot, you may need to enter the data more than once
(see replot).
A blank filename ('') specifies that the previous filename should be reused.
This can be useful with things like
plot 'a/very/long/filename' using 1:2, '' using 1:3, '' using 1:4
(If you use both '-' and '' on the same plot command, you'll need to
have two sets of inline data, as in the example above.)
On some computer systems with a popen function (Unix), the datafile can be
piped through a shell command by starting the file name with a '<'. For
example,
pop(x) = 103*exp(-x/10)
plot "< awk '{print $1-1965, $2}' population.dat", pop(x)
would plot the same information as the first population example but with
years since 1965 as the x axis. If you want to execute this example, you
have to delete all comments from the data file above or substitute the
following command for the first part of the command above (the part up to
the comma):
plot "< awk '$0 !~ /^#/ {print $1-1965, $2}' population.dat"
While this approach is most flexible, it is possible to achieve simple
filtering with the using or thru keywords.
using
The most common datafile modifier is using.
Syntax:
plot 'file' using {<entry> {:<entry> {:<entry> ...}}} {'format'}
If a format is specified, each datafile record is read using the C library's
'scanf' function, with the specified format string. Otherwise the record is
read and broken into columns at spaces or tabs. A format cannot be specified
if time-format data is being used (this must be done by set data time).
The resulting array of data is then sorted into columns according to the
entries. Each <entry> may be a simple column number, which selects the
datum, an expression enclosed in parentheses, or empty. The expression can
use $1 to access the first item read, $2 for the second item, and so on. It
can also use column(x) and valid(x) where x is an arbitrary expression
resulting in an integer. column(x) returns the x'th datum; valid(x)
tests that the datum in the x'th column is a valid number. A column number
of 0 generates a number increasing (from zero) with each point, and is reset
upon encountering two blank records. A column number of -1 gives the
dataline number, which starts at 0, increments at single blank records, and
is reset at double blank records. A column number of -2 gives the index
number, which is incremented only when two blank records are found. An empty
<entry> will default to its order in the list of entries. For example,
using ::4 is interpreted as using 1:2:4.
N.B.---the call command also uses $'s as a special character. See call
for details about how to include a column number in a call argument list.
If the using list has but a single entry, that <entry> will be used for y
and the data point number is used for x; for example, "plot 'file' using 1"
is identical to "plot 'file' using 0:1". If the using list has two
entries, these will be used for x and y. Additional entries are usually
errors in x and/or y. See set style for details about plotting styles that
make use of error information, and fit for use of error information in
curve fitting.
'scanf' accepts several numerical specifications but gnuplot requires all
inputs to be double-precision floating-point variables, so lf is the only
permissible specifier. 'scanf' expects to see white space---a blank, tab
("\t"), newline ("\n"), or formfeed ("\f")---between numbers; anything else
in the input stream must be explicitly skipped.
Note that the use of "\t", "\n", or "\f" or requires use of double-quotes
rather than single-quotes.
Examples:
This creates a plot of the sum of the 2nd and 3rd data against the first:
(The format string specifies comma- rather than space-separated columns.)
plot 'file' using 1:($2+$3) '%lf,%lf,%lf'
In this example the data are read from the file "MyData" using a more
complicated format:
plot 'MyData' using "%*lf%lf%*20[^\n]%lf"
The meaning of this format is:
%*lf ignore a number
%lf read a double-precision number (x by default)
%*20[^\n] ignore 20 non-newline characters
%lf read a double-precision number (y by default)
One trick is to use the ternary ?: operator to filter data:
plot 'file' using 1:($3>10 ? $2 : 1/0)
which plots the datum in column two against that in column one provided
the datum in column three exceeds ten. 1/0 is undefined; gnuplot
quietly ignores undefined points, so unsuitable points are suppressed.
In fact, you can use a constant expression for the column number, provided it
doesn't start with an opening parenthesis; constructs like using
0+(complicated expression) can be used. The crucial point is that the
expression is evaluated once if it doesn't start with a left parenthesis, or
once for each data point read if it does.
If timeseries data are being used, the time can span multiple columns. The
starting column should be specified. Note that the spaces within the time
must be included when calculating starting columns for other data. E.g., if
the first element on a line is a time with an embedded space, the y value
should be specified as column three.
It should be noted that plot 'file', plot 'file' using 1:2, and plot
'file' using ($1):($2) can be subtly different: 1) if file has some lines
with one column and some with two, the first will invent x values when they
are missing, the second will quietly ignore the lines with one column, and
the third will store an undefined value for lines with one point (so that in
a plot with lines, no line joins points across the bad point); 2) if a line
contains text at the first column, the first will abort the plot on an error,
but the second and third should quietly skip the garbage.
In fact, it is often possible to plot a file with lots of lines of garbage at
the top simply by specifying
plot 'file' using 1:2
However, if you want to leave text in your data files, it is safer to put the
comment character (#) in the first column of the text lines.
Feeble using demos.
errorbars
Error bars are supported for 2-d data file plots by reading one to four
additional columns (or using entries); these additional values are used in
different ways by the various errorbar styles.
In the default situation, gnuplot expects to see three, four, or six
numbers on each line of the data file---either
(x, y, ydelta),
(x, y, ylow, yhigh),
(x, y, xdelta),
(x, y, xlow, xhigh),
(x, y, xdelta, ydelta), or
(x, y, xlow, xhigh, ylow, yhigh).
The x coordinate must be specified. The order of the numbers must be
exactly as given above, though the using qualifier can manipulate the order
and provide values for missing columns. For example,
plot 'file' with errorbars
plot 'file' using 1:2:(sqrt($1)) with xerrorbars
plot 'file' using 1:2:($1-$3):($1+$3):4:5 with xyerrorbars
The last example is for a file containing an unsupported combination of
relative x and absolute y errors. The using entry generates absolute x min
and max from the relative error.
The y error bar is a vertical line plotted from (x, ylow) to (x, yhigh).
If ydelta is specified instead of ylow and yhigh, ylow = y - ydelta and
yhigh = y + ydelta are derived. If there are only two numbers on the record,
yhigh and ylow are both set to y. The x error bar is a horizontal line
computed in the same fashion. To get lines plotted between the data points,
plot the data file twice, once with errorbars and once with lines (but
remember to use the notitle option on one to avoid two entries in the key).
The error bars have crossbars at each end unless set bar is used (see set
bar for details).
If autoscaling is on, the ranges will be adjusted to include the error bars.
Errorbar demos.
See plot using, plot with, and set style for more information.
ranges
The optional ranges specify the region of the graph that will be displayed.
Syntax:
[{<dummy-var>=}{{<min>}:{<max>}}]
[{{<min>}:{<max>}}]
The first form applies to the independent variable (xrange or trange, if
in parametric mode). The second form applies to the dependent variable
yrange (and xrange, too, if in parametric mode). <dummy-var> is a new
name for the independent variable. (The defaults may be changed with set
dummy.) The optional <min> and <max> terms can be constant expressions or *.
In non-parametric mode, the order in which ranges must be given is xrange
and yrange.
In parametric mode, the order for the plot command is trange, xrange,
and yrange. The following plot command shows setting the trange to
[-pi:pi], the xrange to [-1.3:1.3] and the yrange to [-1:1] for the
duration of the graph:
plot [-pi:pi] [-1.3:1.3] [-1:1] sin(t),t**2
Note that the x2range and y2range cannot be specified here---set x2range
and set y2range must be used.
Ranges are interpreted in the order listed above for the appropriate mode.
Once all those needed are specified, no further ones must be listed, but
unneeded ones cannot be skipped---use an empty range [] as a placeholder.
* can be used to allow autoscaling of either of min and max. See also
set autoscale.
Ranges specified on the plot or splot command line affect only that
graph; use the set xrange, set yrange, etc., commands to change the
default ranges for future graphs.
With time data, you must provide the range (in the same manner as the time
appears in the datafile) within quotes. gnuplot uses the timefmt string
to read the value---see set timefmt.
Examples:
This uses the current ranges:
plot cos(x)
This sets the x range only:
plot [-10:30] sin(pi*x)/(pi*x)
This is the same, but uses t as the dummy-variable:
plot [t = -10 :30] sin(pi*t)/(pi*t)
This sets both the x and y ranges:
plot [-pi:pi] [-3:3] tan(x), 1/x
This sets only the y range, and turns off autoscaling on both axes:
plot [ ] [-2:sin(5)*-8] sin(x)**besj0(x)
This sets xmax and ymin only:
plot [:200] [-pi:] exp(sin(x))
This sets the x range for a timeseries:
set timefmt "%d/%m/%y %H:%M"
plot ["1/6/93 12:00":"5/6/93 12:00"] 'timedata.dat'
See Demo.
title
A line title for each function and data set appears in the key, accompanied
by a sample of the line and/or symbol used to represent it. It can be
changed by using the title option.
Syntax:
title "<title>" | notitle
where <title> is the new title of the line and must be enclosed in quotes.
The quotes will not be shown in the key. A special character may be given as
a backslash followed by its octal value ("\345"). The tab character "\t" is
understood. Note that backslash processing occurs only for strings enclosed
in double quotes---use single quotes to prevent such processing. The newline
character "\n" is not processed in key entries in either type of string.
The line title and sample can be omitted from the key by using the keyword
notitle. A null title (title '') is equivalent to notitle. If only
the sample is wanted, use one or more blanks (title ' ').
By default the line title is the function or file name as it appears on the
plot command. If it is a file name, any datafile modifiers specified will
be included in the default title.
The layout of the key itself (position, title justification, etc.) can be
controlled by set key. Please see set key for details.
Examples:
This plots y=x with the title 'x':
plot x
This plots x squared with title "x^2" and file "data.1" with title
"measured data":
plot x**2 title "x^2", 'data.1' t "measured data"
This puts an untitled circular border around a polar graph:
set polar; plot my_function(t), 1 notitle
with
Functions and data may be displayed in one of a large number of styles.
The with keyword provides the means of selection.
Syntax:
with <style> { {linestyle | ls <line_style>}
| {{linetype | lt <line_type>}
{linewidth | lw <line_width>}
{pointtype | pt <point_type>}
{pointsize | ps <point_size>}} }
where <style> is either lines, points, linespoints, impulses, dots,
steps, fsteps, histeps, errorbars, xerrorbars, yerrorbars,
xyerrorbars, boxes, boxerrorbars, boxxyerrorbars, financebars,
candlesticks or vector. Some of these styles require additional
information. See set style <style> for details of each style.
Default styles are chosen with the set function style and set data style
commands.
By default, each function and data file will use a different line type and
point type, up to the maximum number of available types. All terminal
drivers support at least six different point types, and re-use them, in
order, if more are required. The LaTeX driver supplies an additional six
point types (all variants of a circle), and thus will only repeat after 12
curves are plotted with points. The PostScript drivers (postscript)
supplies a total of 64.
If you wish to choose the line or point type for a single plot, <line_type>
and <point_type> may be specified. These are positive integer constants (or
expressions) that specify the line type and point type to be used for the
plot. Use test to display the types available for your terminal.
You may also scale the line width and point size for a plot by using
<line_width> and <point_size>, which are specified relative to the default
values for each terminal. The pointsize may also be altered globally---see
set pointsize for details. But note that both <point_size> as set here and
as set by set pointsize multiply the default point size---their effects are
not cumulative. That is, set pointsize 2; plot x w p ps 3 will use points
three times default size, not six.
If you have defined specific line type/width and point type/size combinations
with set linestyle, one of these may be selected by setting <line_style> to
the index of the desired style.
The keywords may be abbreviated as indicated.
Note that the linewidth and pointsize options are not supported by all
terminals.
Examples:
This plots sin(x) with impulses:
plot sin(x) with impulses
This plots x with points, x**2 with the default:
plot x*y w points, x**2 + y**2
This plots tan(x) with the default function style, file "data.1" with lines:
plot [ ] [-2:5] tan(x), 'data.1' with l
This plots "leastsq.dat" with impulses:
plot 'leastsq.dat' w i
This plots the data file "population" with boxes:
plot 'population' with boxes
This plots "exper.dat" with errorbars and lines connecting the points
(errorbars require three or four columns):
plot 'exper.dat' w lines, 'exper.dat' notitle w errorbars
This plots sin(x) and cos(x) with linespoints, using the same line type but
different point types:
plot sin(x) with linesp lt 1 pt 3, cos(x) with linesp lt 1 pt 4
This plots file "data" with points of type 3 and twice usual size:
plot 'data' with points pointtype 3 pointsize 2
This plots two data sets with lines differing only by weight:
plot 'd1' t "good" w l lt 2 lw 3, 'd2' t "bad" w l lt 2 lw 1
See set style to change the default styles.
Styles demos.
reread
The reread command causes the current gnuplot command file, as specified
by a load command or on the command line, to be reset to its starting
point before further commands are read from it. This essentially implements
an endless loop of the commands from the beginning of the command file to
the reread command. (But this is not necessarily a disaster---reread can
be very useful when used in conjunction with if. See if for details.)
The reread command has no effect if input from standard input.
Examples:
Suppose the file "looper" contains the commands
a=a+1
plot sin(x*a)
pause -1
if(a<5) reread
and from within gnuplot you submit the commands
a=0
load 'looper'
The result will be four plots (separated by the pause message).
Suppose the file "data" contains six columns of numbers with a total yrange
from 0 to 10; the first is x and the next are five different functions of x.
Suppose also that the file "plotter" contains the commands
c_p = c_p+1
plot "$0" using 1:c_p with lines linetype c_p
if(c_p < n_p) reread
and from within gnuplot you submit the commands
n_p=6
c_p=1
set nokey
set yrange [0:10]
set multiplot
call 'plotter' 'data'
set nomultiplot
The result is a single graph consisting of five plots. The yrange must be
set explicitly to guarantee that the five separate graphs (drawn on top of
each other in multiplot mode) will have exactly the same axes. The linetype
must be specified; otherwise all the plots would be drawn with the same type.
Reread Animation Demo
angles
By default, gnuplot assumes the independent variable in polar graphs is in
units of radians. If set angles degrees is specified before set polar,
then the default range is [0:360] and the independent variable has units of
degrees. This is particularly useful for plots of data files. The angle
setting also applies to 3-d mapping as set via the set mapping command.
Syntax:
set angles {degrees | radians}
show angles
The angle specified in set grid polar is also read and displayed in the
units specified by set angles.
set angles also affects the arguments of the machine-defined functions
sin(x), cos(x) and tan(x), and the outputs of asin(x), acos(x), atan(x),
atan2(x), and arg(x). It has no effect on the arguments of hyperbolic
functions or Bessel functions. However, the output arguments of inverse
hyperbolic functions of complex arguments are affected; if these functions
are used, set angles radians must be in effect to maintain consistency
between input and output arguments.
x={1.0,0.1}
set angles radians
y=sinh(x)
print y #prints {1.16933, 0.154051}
print asinh(y) #prints {1.0, 0.1}
but
set angles degrees
y=sinh(x)
print y #prints {1.16933, 0.154051}
print asinh(y) #prints {57.29578, 5.729578}
Polar plot using `set angles`.
arrow
Arbitrary arrows can be placed on a plot using the set arrow command.
Syntax:
set arrow {<tag>} {from <position>} {to <position>} {{no}head}
{ {linestyle | ls <line_style>}
| {linetype | lt <line_type>}
{linewidth | lw <line_width} }
set noarrow {<tag>}
show arrow
<tag> is an integer that identifies the arrow. If no tag is given, the
lowest unused tag value is assigned automatically. The tag can be used to
delete or change a specific arrow. To change any attribute of an existing
arrow, use the set arrow command with the appropriate tag and specify the
parts of the arrow to be changed.
The <position>s are specified by either x,y or x,y,z, and may be preceded by
first, second, graph, or screen to select the coordinate system.
Unspecified coordinates default to 0. The endpoints can be specified in
one of four coordinate systems---first or second axes, graph or
screen. See coordinates for details. A coordinate system specifier
does not carry over from the "from" position to the "to" position. Arrows
outside the screen boundaries are permitted but may cause device errors.
Specifying nohead produces an arrow drawn without a head---a line segment.
This gives you yet another way to draw a line segment on the plot. By
default, arrows have heads.
The line style may be selected from a user-defined list of line styles (see
set linestyle) or may be defined here by providing values for <line_type>
(an index from the default list of styles) and/or <line_width> (which is a
multiplier for the default width).
Note, however, that if a user-defined line style has been selected, its
properties (type and width) cannot be altered merely by issuing another
set arrow command with the appropriate index and lt or lw.
Examples:
To set an arrow pointing from the origin to (1,2) with user-defined style 5,
use:
set arrow to 1,2 ls 5
To set an arrow from bottom left of plotting area to (-5,5,3), and tag the
arrow number 3, use:
set arrow 3 from graph 0,0 to -5,5,3
To change the preceding arrow to end at 1,1,1, without an arrow head and
double its width, use:
set arrow 3 to 1,1,1 nohead lw 2
To draw a vertical line from the bottom to the top of the graph at x=3, use:
set arrow from 3, graph 0 to 3, graph 1 nohead
To delete arrow number 2, use:
set noarrow 2
To delete all arrows, use:
set noarrow
To show all arrows (in tag order), use:
show arrow
Arrows Demos.
autoscale
Autoscaling may be set individually on the x, y or z axis or globally on all
axes. The default is to autoscale all axes.
Syntax:
set autoscale {<axes>{min|max}}
set noautoscale {<axes>{min|max}}
show autoscale
where <axes> is either x, y, z, x2, y2 or xy. A keyword with
min or max appended (this cannot be done with xy) tells gnuplot to
autoscale just the minimum or maximum of that axis. If no keyword is given,
all axes are autoscaled.
When autoscaling, the axis range is automatically computed and the dependent
axis (y for a plot and z for splot) is scaled to include the range of the
function or data being plotted.
If autoscaling of the dependent axis (y or z) is not set, the current y or z
range is used.
Autoscaling the independent variables (x for plot and x,y for splot) is a
request to set the domain to match any data file being plotted. If there are
no data files, autoscaling an independent variable has no effect. In other
words, in the absence of a data file, functions alone do not affect the x
range (or the y range if plotting z = f(x,y)).
Please see set xrange for additional information about ranges.
The behavior of autoscaling remains consistent in parametric mode, (see set
parametric). However, there are more dependent variables and hence more
control over x, y, and z axis scales. In parametric mode, the independent or
dummy variable is t for plots and u,v for splots. autoscale in
parametric mode, then, controls all ranges (t, u, v, x, y, and z) and allows
x, y, and z to be fully autoscaled.
Autoscaling works the same way for polar mode as it does for parametric mode
for plot, with the extension that in polar mode set dummy can be used to
change the independent variable from t (see set dummy).
When tics are displayed on second axes but no plot has been specified for
those axes, x2range and y2range are inherited from xrange and yrange. This
is done _before_ xrange and yrange are autoextended to a whole number of
tics, which can cause unexpected results.
Examples:
This sets autoscaling of the y axis (other axes are not affected):
set autoscale y
This sets autoscaling only for the minimum of the y axis (the maximum of the
y axis and the other axes are not affected):
set autoscale ymin
This sets autoscaling of the x and y axes:
set autoscale xy
This sets autoscaling of the x, y, z, x2 and y2 axes:
set autoscale
This disables autoscaling of the x, y, z, x2 and y2 axes:
set noautoscale
This disables autoscaling of the z axis only:
set noautoscale z
parametric mode
polar mode
border
The set border and set noborder commands control the display of the graph
borders for the plot and splot commands.
Syntax:
set border {<integer> { {linestyle | ls <line_style>}
| {linetype | lt <line_type> }
{linewidth | lw <line_width>} } }
set noborder
show border
The borders are encoded in a 12-bit integer: the bottom four bits control the
border for plot and the sides of the base for splot; The next four bits
control the verticals in splot; the top four bits control the edges on top
of the splot. In detail, the <integer> should be the sum of the
appropriate entries from the following table:
plot border splot splot
Side splot base verticals top
bottom (south) 1 16 256
left (west) 2 32 512
top (north) 4 64 1024
right (east) 8 128 2048
The default is 31, which is all four sides for plot, and base and z axis
for splot.
Using the optional <line_style>, <line_type> and <line_width>
specifiers, the way the border lines are drawn can be influenced
(limited by what the current terminal driver supports). By default,
the border is drawn with twice the usual linewidth. The <line_width>
specifier scales this default value; for example, set border 15 lw 2
will produce a border with four times the usual linewidth.
Various axes or combinations of axes may be added together in the command.
To have tics on edges other than bottom and left, disable the usual tics and
enable the second axes.
Examples:
Draw all borders:
set border
Draw only the SOUTHWEST borders:
set border 3
Draw a complete box around a splot:
set border 4095
Draw a partial box, omitting the front vertical:
set border 127+256+512
Draw only the NORTHEAST borders:
set noxtics; set noytics; set x2tics; set y2tics; set border 12
Borders Demo.
clip
gnuplot can clip data points and lines that are near the boundaries of a
graph.
Syntax:
set clip <clip-type>
set noclip <clip-type>
show clip
Three clip types are supported by gnuplot: points, one, and two.
One, two, or all three clip types may be active for a single graph.
The points clip type forces gnuplot to clip (actually, not plot at all)
data points that fall within but too close to the boundaries. This is done
so that large symbols used for points will not extend outside the boundary
lines. Without clipping points near the boundaries, the plot may look bad.
Adjusting the x and y ranges may give similar results.
Setting the one clip type causes gnuplot to draw a line segment which has
only one of its two endpoints within the graph. Only the in-range portion of
the line is drawn. The alternative is to not draw any portion of the line
segment.
Some lines may have both endpoints out of range, but pass through the graph.
Setting the two clip-type allows the visible portion of these lines to be
drawn.
In no case is a line drawn outside the graph.
The defaults are noclip points, clip one, and noclip two.
To check the state of all forms of clipping, use
show clip
For backward compatibility with older versions, the following forms are also
permitted:
set clip
set noclip
set clip is synonymous with set clip points; set noclip turns off all
three types of clipping.
cntrparam
set cntrparam controls the generation of contours and their smoothness for
a contour plot. show contour displays current settings of cntrparam as
well as contour.
Syntax:
set cntrparam { {linear | cubicspline | bspline}
{ points <n>} { order <n> }
{ levels auto {<n>} | <n>
| discrete <z1> {,<z2>{,<z3>...}}
| incremental <start>, <incr> {,<end>}
}
}
show contour
This command has two functions. First, it sets the values of z for which
contour points are to be determined (by linear interpolation between data
points or function isosamples.) Second, it controls the way contours are
drawn between the points determined to be of equal z. <n> should be an
integral constant expression and <z1>, <z2> ... any constant expressions.
The parameters are:
linear, cubicspline, bspline---Controls type of approximation or
interpolation. If linear, then straight line segments connect points of
equal z magnitude. If cubicspline, then piecewise-linear contours are
interpolated between the same equal z points to form somewhat smoother
contours, but which may undulate. If bspline, a guaranteed-smoother curve
is drawn, which only approximates the position of the points of equal-z.
points---Eventually all drawings are done with piecewise-linear strokes.
This number controls the number of line segments used to approximate the
bspline or cubicspline curve. Number of cubicspline or bspline
segments (strokes) = points * number of linear segments.
order---Order of the bspline approximation to be used. The bigger this
order is, the smoother the resulting contour. (Of course, higher order
bspline curves will move further away from the original piecewise linear
data.) This option is relevant for bspline mode only. Allowed values are
integers in the range from 2 (linear) to 10.
levels--- Selection of contour levels, controlled by auto (default),
discrete, incremental, and <n>, number of contour levels, limited to
MAX_DISCRETE_LEVELS as defined in plot.h (30 is standard.)
For auto, <n> specifies a nominal number of levels; the actual number will
be adjusted to give simple labels. If the surface is bounded by zmin and zmax,
contours will be generated at integer multiples of dz between zmin and zmax,
where dz is 1, 2, or 5 times some power of ten (like the step between two
tic marks).
For levels discrete, contours will be generated at z = <z1>, <z2> ... as
specified; the number of discrete levels sets the number of contour levels.
In discrete mode, any set cntrparms levels <n> are ignored.
For incremental, contours are generated at values of z beginning at <start>
and increasing by <increment>, until the number of contours is reached. <end>
is used to determine the number of contour levels, which will be changed by
any subsequent set cntrparam levels <n>.
If the command set cntrparam is given without any arguments specified, the
defaults are used: linear, 5 points, order 4, 5 auto levels.
Examples:
set cntrparam bspline
set cntrparam points 7
set cntrparam order 10
To select levels automatically, 5 if the level increment criteria are met:
set cntrparam levels auto 5
To specify discrete levels at .1, .37, and .9:
set cntrparam levels discrete .1,1/exp(1),.9
To specify levels from 0 to 4 with increment 1:
set cntrparam levels incremental 0,1,4
To set the number of levels to 10 (changing an incremental end or possibly
the number of auto levels):
set cntrparam levels 10
To set the start and increment while retaining the number of levels:
set cntrparam levels incremental 100,50
See also set contour for control of where the contours are drawn, and set
clabel for control of the format of the contour labels and linetypes.
Contours Demo and
contours with User Defined Levels.
contour
set contour enables contour drawing for surfaces. This option is available
for splot only.
Syntax:
set contour {base | surface | both}
set nocontour
show contour
The three options specify where to draw the contours: base draws the
contours on the grid base where the x/ytics are placed, surface draws the
contours on the surfaces themselves, and both draws the contours on both
the base and the surface. If no option is provided, the default is base.
See also set cntrparam for the parameters that affect the drawing of
contours, and set clabel for control of labelling of the contours.
The surface can be switched off (see set surface), giving a contour-only
graph. Though it is possible to use set size to enlarge the plot to fill
the screen, more control over the output format can be obtained by writing
the contour information to a file, and rereading it as a 2-d datafile plot:
set nosurface
set contour
set cntrparam ...
set term table
set out 'filename'
splot ...
set out
# contour info now in filename
set term <whatever>
plot 'filename'
In order to draw contours, the data should be organized as "grid data". In
such a file all the points for a single y-isoline are listed, then all the
points for the next y-isoline, and so on. A single blank line (a line
containing no characters other than blank spaces and a carriage return and/or
a line feed) separates one y-isoline from the next. See also splot datafile.
If contours are desired from non-grid data, set dgrid3d can be used to
create an appropriate grid. See set dgrid3d for more information.
Contours Demo and
contours with User Defined Levels.
dgrid3d
The set dgrid3d command enables, and can set parameters for, non-grid
to grid data mapping.
Syntax:
set dgrid3d {<row_size>} {,{<col_size>} {,<norm>}}
set nodgrid3d
show dgrid3d
By default dgrid3d is disabled. When enabled, 3-d data read from a file
are always treated as a scattered data set. A grid with dimensions derived
from a bounding box of the scattered data and size as specified by the
row/col_size parameters is created for plotting and contouring. The grid
is equally spaced in x (rows) and in y (columns); the z values are computed
as weighted averages of the scattered points' z values.
The third parameter, norm, controls the weighting: Each data point is
weighted inversely by its distance from the grid point raised to the norm
power. (Actually, the weights are given by the inverse of dx^norm + dy^norm,
where dx and dy are the components of the separation of the grid point from
each data point. For some norms that are powers of two, specifically 4, 8,
and 16, the computation is optimized by using the Euclidean distance in the
weight calculation, (dx^2+dx^2)^norm/2. However, any non-negative integer
can be used.)
The closer the data point is to a grid point, the more effect it has on
that grid point and the larger the value of norm the less effect more
distant data points have on that grid point.
The dgrid3d option is a simple low pass filter that converts scattered
data to a grid data set. More sophisticated approaches to this problem
exist and should be used to preprocess the data outside gnuplot if this
simple solution is found inadequate.
(The z values are found by weighting all data points, not by interpolating
between nearby data points; also edge effects may produce unexpected and/or
undesired results. In some cases, small norm values produce a grid point
reflecting the average of distant data points rather than a local average,
while large values of norm may produce "steps" with several grid points
having the same value as the closest data point, rather than making a smooth
transition between adjacent data points. Some areas of a grid may be filled
by extrapolation, to an arbitrary boundary condition. The variables are
not normalized; consequently the units used for x and y will affect the
relative weights of points in the x and y directions.)
Examples:
set dgrid3d 10,10,1 # defaults
set dgrid3d ,,4
The first specifies that a grid of size 10 by 10 is to be constructed using
a norm value of 1 in the weight computation. The second only modifies the
norm, changing it to 4.
Dgrid3d Demo.
dummy
The set dummy command changes the default dummy variable names.
Syntax:
set dummy {<dummy-var>} {,<dummy-var>}
show dummy
By default, gnuplot assumes that the independent, or "dummy", variable for
the plot command is "t" if in parametric or polar mode, or "x" otherwise.
Similarly the independent variables for the splot command are "u" and "v"
in parametric mode (splot cannot be used in polar mode), or "x" and "y"
otherwise.
It may be more convenient to call a dummy variable by a more physically
meaningful or conventional name. For example, when plotting time functions:
set dummy t
plot sin(t), cos(t)
At least one dummy variable must be set on the command; set dummy by itself
will generate an error message.
Examples:
set dummy u,v
set dummy ,s
The second example sets the second variable to s.
format
The format of the tic-mark labels can be set with the set format command.
Syntax:
set format {<axes>} {"<format-string>"}
set format {<axes>} {'<format-string>'}
show format
where <axes> is either x, y, z, xy, x2, y2 or nothing (which is
the same as xy). The length of the string representing a tic mark (after
formatting with 'printf') is restricted to 100 characters. If the format
string is omitted, the format will be returned to the default "%g". For
LaTeX users, the format "$%g$" is often desirable. If the empty string "" is
used, no label will be plotted with each tic, though the tic mark will still
be plotted. To eliminate all tic marks, use set noxtics or set noytics.
Newline (\n) is accepted in the format string. Use double-quotes rather than
single-quotes to enable such interpretation. See also syntax.
The default format for both axes is "%g", but other formats such as "%.2f" or
"%3.0em" are often desirable. Anything accepted by 'printf' when given a
double precision number, and accepted by the terminal, will work. Some other
options have been added. If the format string looks like a floating point
format, then gnuplot tries to construct a reasonable format.
Characters not preceded by "%" are printed verbatim. Thus you can include
spaces and labels in your format string, such as "%g m", which will put " m"
after each number. If you want "%" itself, double it: "%g %%".
See also set xtics for more information about tic labels.
See demo.
format specifiers
time/date specifiers
format specifiers
The acceptable formats (if not in time/date mode) are:
Format Explanation
%f floating point notation
%e or %E exponential notation; an "e" or "E" before the power
%g or %G the shorter of %e (or %E) and %f
%x or %X hex
%o or %O octal
%t mantissa to base 10
%l mantissa to base of current logscale
%s mantissa to base of current logscale; scientific power
%T power to base 10
%L power to base of current logscale
%S scientific power
%c character replacement for scientific power
%P multiple of pi
A 'scientific' power is one such that the exponent is a multiple of three.
Character replacement of scientific powers ("%c") has been implemented
for powers in the range -18 to +18. For numbers outside of this range the
format reverts to exponential.
Other acceptable modifiers (which come after the "%" but before the format
specifier) are "-", which left-justifies the number; "+", which forces all
numbers to be explicitly signed; "#", which places a decimal point after
floats that have only zeroes following the decimal point; a positive integer,
which defines the field width; "0" (the digit, not the letter) immediately
preceding the field width, which indicates that leading zeroes are to be used
instead of leading blanks; and a decimal point followed by a non-negative
integer, which defines the precision (the minimum number of digits of an
integer, or the number of digits following the decimal point of a float).
Some releases of 'printf' may not support all of these modifiers but may also
support others; in case of doubt, check the appropriate documentation and
then experiment.
Examples:
set format y "%t"; set ytics (5,10) # "5.0" and "1.0"
set format y "%s"; set ytics (500,1000) # "500" and "1.0"
set format y "+-12.3f"; set ytics(12345) # "+12345.000 "
set format y "%.2t*10^%+03T"; set ytic(12345)# "1.23*10^+04"
set format y "%s*10^{%S}"; set ytic(12345) # "12.345*10^{3}"
set format y "%s %cg"; set ytic(12345) # "12.345 kg"
set format y "%.0P pi"; set ytic(6.283185) # "2 pi"
set format y "%.0P%%"; set ytic(50) # "50%"
set log y 2; set format y '%l'; set ytics (1,2,3)
#displays "1.0", "1.0" and "1.5" (since 3 is 1.5 * 2^1)
There are some problem cases that arise when numbers like 9.999 are printed
with a format that requires both rounding and a power.
If the data type for the axis is time/date, the format string must contain
valid codes for the 'strftime' function (outside of gnuplot, type "man
strftime"). See set timefmt for a list of the allowed input format codes.
time/date specifiers
In time/date mode, the acceptable formats are:
Format Explanation
%a abbreviated name of day of the week
%A full name of day of the week
%b or %h abbreviated name of the month
%B full name of the month
%d day of the month, 1--31
%D shorthand for "%m/%d/%y"
%H or %k hour, 0--24
%I or %l hour, 0--12
%j day of the year, 1--366
%m month, 1--12
%M minute, 0--60
%p "am" or "pm"
%r shorthand for "%I:%M:%S %p"
%R shorthand for %H:%M"
%S second, 0--60
%T shorthand for "%H:%M:%S"
%U week of the year (week starts on Sunday)
%w day of the week, 0--6 (Sunday = 0)
%W week of the year (week starts on Monday)
%y year, 0-99
%Y year, 4-digit
Except for the non-numerical formats, these may be preceded by a "0" ("zero",
not "oh") to pad the field length with leading zeroes, and a positive digit,
to define the minimum field width (which will be overridden if the specified
width is not large enough to contain the number). There is a 24-character
limit to the length of the printed text; longer strings will be truncated.
Examples:
Suppose the text is "76/12/25 23:11:11". Then
set format x # defaults to "12/25/76" \n "23:11"
set format x "%A, %d %b %Y" # "Saturday, 25 Dec 1976"
set format x "%r %d" # "11:11:11 pm 12/25/76"
Suppose the text is "98/07/06 05:04:03". Then
set format x "%1y/%2m/%3d %01H:%02M:%03S" # "98/ 7/ 6 5:04:003"
grid
The set grid command allows grid lines to be drawn on the plot.
Syntax:
set grid {{no}{m}xtics} {{no}{m}ytics} {{no}{m}ztics}
{{no}{m}x2tics} {{no}{m}y2tics}
{polar {<angle>}}
{ {linestyle <major_linestyle>}
| {linetype | lt <major_linetype>}
{linewidth | lw <major_linewidth>}
{ , {linestyle | ls <minor_linestyle>}
| {linetype | lt <minor_linetype>}
{linewidth | lw <minor_linewidth>} } }
set nogrid
show grid
The grid can be enabled and disabled for the major and/or minor tic
marks on any axis, and the linetype and linewidth can be specified
for major and minor grid lines, also via a predefined linestyle, as
far as the active terminal driver supports this.
Additionally, a polar grid can be selected for 2-d plots---circles are drawn
to intersect the selected tics, and radial lines are drawn at definable
intervals. (The interval is given in degrees or radians ,depending on the
set angles setting.) Note that a polar grid is no longer automatically
generated in polar mode.
The pertinent tics must be enabled before set grid can draw them; gnuplot
will quietly ignore instructions to draw grid lines at non-existent tics, but
they will appear if the tics are subsequently enabled.
If no linetype is specified for the minor gridlines, the same linetype as the
major gridlines is used. The default polar angle is 30 degrees.
By default, grid lines are drawn with half the usual linewidth. The major and
minor linewidth specifiers scale this default value; for example, set grid
lw .5 will draw grid lines with one quarter the usual linewidth.
Z grid lines are drawn on the back of the plot. This looks better if a
partial box is drawn around the plot---see set border.
hidden3d
The set hidden3d command enables hidden line removal for surface plotting
(see splot). Some optional features of the underlying algorithm can also
be controlled using this command.
Syntax:
set hidden3d {defaults} |
{ {{offset <offset>} | {nooffset}}
{trianglepattern <bitpattern>}
{{undefined <level>} | {noundefined}}
{{no}altdiagonal}
{{no}bentover} }
set nohidden3d
show hidden3d
In contrast to the usual display in gnuplot, hidden line removal actually
treats the given function or data grids as real surfaces that can't be seen
through, so parts behind the surface will be hidden by it. For this to be
possible, the surface needs to have 'grid structure' (see splot datafile
about this), and it has to be drawn with lines or with linespoints.
When hidden3d is set, both the hidden portion of the surface and possibly
its contours drawn on the base (see set contour) as well as the grid will
be hidden. Each surface has its hidden parts removed with respect to itself
and to other surfaces, if more than one surface is plotted. Contours drawn
on the surface (set contour surface) don't work. Labels and arrows are
always visible and are unaffected. The key is also never hidden by the
surface.
Functions are evaluated at isoline intersections. The algorithm interpolates
linearly between function points or data points when determining the visible
line segments. This means that the appearance of a function may be different
when plotted with hidden3d than when plotted with nohidden3d because in
the latter case functions are evaluated at each sample. Please see set
samples and set isosamples for discussion of the difference.
The algorithm used to remove the hidden parts of the surfaces has some
additional features controllable by this command. Specifying defaults will
set them all to their default settings, as detailed below. If defaults is
not given, only explicitly specified options will be influenced: all others
will keep their previous values, so you can turn on/off hidden line removal
via set {no}hidden3d, without modifying the set of options you chose.
The first option, offset, influences the linestyle used for lines on the
'back' side. Normally, they are drawn in a linestyle one index number higher
than the one used for the front, to make the two sides of the surface
distinguishable. You can specify a different line style offset to add
instead of the default 1, by offset <offset>. Option nooffset stands for
offset 0, making the two sides of the surface use the same linestyle.
Next comes the option trianglepattern <bitpattern>. <bitpattern> must be
a number between 0 and 7, interpreted as a bit pattern. Each bit determines
the visibility of one edge of the triangles each surface is split up into.
Bit 0 is for the 'horizontal' edges of the grid, Bit 1 for the 'vertical'
ones, and Bit 2 for the diagonals that split each cell of the original grid
into two triangles. The default pattern is 3, making all horizontal and
vertical lines visible, but not the diagonals. You may want to choose 7 to
see those diagonals as well.
The undefined <level> option lets you decide what the algorithm is to do
with data points that are undefined (missing data, or undefined function
values), or exceed the given x-, y- or z-ranges. Such points can either be
plotted nevertheless, or taken out of the input data set. All surface
elements touching a point that is taken out will be taken out as well, thus
creating a hole in the surface. If <level> = 3, equivalent to option
noundefined, no points will be thrown away at all. This may produce all
kinds of problems elsewhere, so you should avoid this. <level> = 2 will
throw away undefined points, but keep the out-of-range ones. <level> = 1,
the default, will get rid of out-of-range points as well.
By specifying noaltdiagonal, you can override the default handling of a
special case can occur if undefined is active (i.e. <level> is not 3).
Each cell of the grid-structured input surface will be divided in two
triangles along one of its diagonals. Normally, all these diagonals have
the same orientation relative to the grid. If exactly one of the four cell
corners is excluded by the undefined handler, and this is on the usual
diagonal, both triangles will be excluded. However if the default setting
of altdiagonal is active, the other diagonal will be chosen for this cell
instead, minimizing the size of the hole in the surface.
The bentover option controls what happens to another special case, this
time in conjunction with the trianglepattern. For rather crumply surfaces,
it can happen that the two triangles a surface cell is divided into are seen
from opposite sides (i.e. the original quadrangle is 'bent over'), as
illustrated in the following ASCII art:
C----B
original quadrangle: A--B displayed quadrangle: |\ |
("set view 0,0") | /| ("set view 75,75" perhaps) | \ |
|/ | | \ |
C--D | \|
A D
If the diagonal edges of the surface cells aren't generally made visible by
bit 2 of the <bitpattern> there, the edge CB above wouldn't be drawn at all,
normally, making the resulting display hard to understand. Therefore, the
default option of bentover will turn it visible in this case. If you don't
want that, you may choose nobentover instead.
Hidden Line Removal Demo and
Complex Hidden Line Demo.
key
The set key enables a key (or legend) describing plots on a plot.
The contents of the key, i.e., the names given to each plotted data set and
function and samples of the lines and/or symbols used to represent them, are
determined by the title and with options of the {s}plot command.
Please see plot title and plot with for more information.
Syntax:
set key { left | right | top | bottom | outside | below
| <position>}
{Left | Right} {{no}reverse}
{samplen <sample_length>} {spacing <vertical_spacing>}
{width <width_increment>}
{title "<text>"}
{{no}box { {linestyle | ls <line_style>}
| {linetype | lt <line_type>}
{linewidth | lw <line_width>}}}
set nokey
show key
By default the key is placed in the upper right corner of the graph. The
keywords left, right, top, bottom, outside and below may be used
to place the key in the other corners inside the graph or to the right
(outside) or below the graph. They may be given alone or combined.
Justification of the labels within the key is controlled by Left or Right
(default is Right). The text and sample can be reversed (reverse) and a
box can be drawn around the key (box {...}) in a specified linetype
and linewidth, or a user-defined linestyle. Note that not all
terminal drivers support linewidth selection, though.
The length of the sample line can be controlled by samplen. The sample
length is computed as the sum of the tic length and <sample_length> times the
character width. samplen also affects the positions of point samples in
the key since these are drawn at the midpoint of the sample line, even if it
is not drawn. <sample_length> must be an integer.
The vertical spacing between lines is controlled by spacing. The spacing
is set equal to the product of the pointsize, the vertical tic size, and
<vertical_spacing>. The program will guarantee that the vertical spacing is
no smaller than the character height.
The <width_increment> is a number of character widths to be added to or
subtracted from the length of the string. This is useful only when you are
putting a box around the key and you are using control characters in the text.
gnuplot simply counts the number of characters in the string when computing
the box width; this allows you to correct it.
A title can be put on the key (title "<text>")---see also syntax for the
distinction between text in single- or double-quotes. The key title uses the
same justification as do the plot titles.
The defaults for set key are right, top, Right, noreverse, samplen
4, spacing 1.25, title "", and nobox. The default <linetype> is the
same as that used for the plot borders. Entering set key with no options
returns the key to its default configuration.
The <position> can be a simple x,y,z as in previous versions, but these can
be preceded by one of four keywords (first, second, graph, screen)
which selects the coordinate system in which the position is specified. See
coordinates for more details.
The key is drawn as a sequence of lines, with one plot described on each
line. On the right-hand side (or the left-hand side, if reverse is
selected) of each line is a representation that attempts to mimic the way the
curve is plotted. On the other side of each line is the text description
(the line title), obtained from the plot command. The lines are vertically
arranged so that an imaginary straight line divides the left- and right-hand
sides of the key. It is the coordinates of the top of this line that are
specified with the set key command. In a plot, only the x and y
coordinates are used to specify the line position. For a splot, x, y and
z are all used as a 3-d location mapped using the same mapping as the graph
itself to form the required 2-d screen position of the imaginary line.
Some or all of the key may be outside of the graph boundary, although this
may interfere with other labels and may cause an error on some devices. If
you use the keywords outside or below, gnuplot makes space for the keys
and the graph becomes smaller. Putting keys outside to the right, they
occupy as few columns as possible, and putting them below, as many columns as
possible (depending of the length of the labels), thus stealing as little
space from the graph as possible.
When using the TeX or PostScript drivers, or similar drivers where formatting
information is embedded in the string, gnuplot is unable to calculate
correctly the width of the string for key positioning. If the key is to be
positioned at the left, it may be convenient to use the combination set key
left Left reverse. The box and gap in the grid will be the width of the
literal string.
If splot is being used to draw contours, the contour labels will be listed
in the key. If the alignment of these labels is poor or a different number
of decimal places is desired, the label format can be specified. See set
clabel for details.
Examples:
This places the key at the default location:
set key
This disables the key:
set nokey
This places a key at coordinates 2,3.5,2 in the default (first) coordinate
system:
set key 2,3.5,2
This places the key below the graph:
set key below
This places the key in the bottom left corner, left-justifies the text,
gives it a title, and draws a box around it in linetype 3:
set key left bottom Left title 'Legend' box 3
label
Arbitrary labels can be placed on the plot using the set label command.
Syntax:
set label {<tag>} {"<label_text>"} {at <position>}
{<justification>} {{no}rotate} {font "<name><,size>"}
set nolabel {<tag>}
show label
The <position> is specified by either x,y or x,y,z, and may be preceded by
first, second, graph, or screen to select the coordinate system.
See coordinates for details.
The tag is an integer that is used to identify the label. If no <tag> is
given, the lowest unused tag value is assigned automatically. The tag can be
used to delete or modify a specific label. To change any attribute of an
existing label, use the set label command with the appropriate tag, and
specify the parts of the label to be changed.
By default, the text is placed flush left against the point x,y,z. To adjust
the way the label is positioned with respect to the point x,y,z, add the
parameter <justification>, which may be left, right or center,
indicating that the point is to be at the left, right or center of the text.
Labels outside the plotted boundaries are permitted but may interfere with
axis labels or other text.
If rotate is given, the label is written vertically (if the terminal can do
so, of course).
If one (or more) axis is timeseries, the appropriate coordinate should be
given as a quoted time string according to the timefmt format string. See
set xdata and set timefmt.
The EEPIC, Imagen, LaTeX, and TPIC drivers allow \\ in a string to specify
a newline.
Examples:
To set a label at (1,2) to "y=x", use:
set label "y=x" at 1,2
To set a Sigma of size 24, from the Symbol font set, at the center of
the graph, use:
set label "S" at graph 0.5,0.5 center font "Symbol,24"
To set a label "y=x^2" with the right of the text at (2,3,4), and tag the
label as number 3, use:
set label 3 "y=x^2" at 2,3,4 right
To change the preceding label to center justification, use:
set label 3 center
To delete label number 2, use:
set nolabel 2
To delete all labels, use:
set nolabel
To show all labels (in tag order), use:
show label
To set a label on a graph with a timeseries on the x axis, use, for example:
set timefmt "%d/%m/%y,%H:%M"
set label "Harvest" at "25/8/93",1
linestyle
Each terminal has a default set of line and point types, which can be seen
by using the command test. set linestyle defines a set of line types
and widths and point types and sizes so that you can refer to them later by
an index instead of repeating all the information at each invocation.
Syntax:
set linestyle <index> {linetype | lt <line_type>}
{linewidth | lw <line_width>}
{pointtype | pt <point_type>}
{pointsize | ps <point_size>}
set nolinestyle
show linestyle
The line and point types are taken from the default types for the terminal
currently in use. The line width and point size are multipliers for the
default width and size (but note that <point_size> here is unaffected by
the multiplier given on 'set pointsize').
The defaults for the line and point types is the index. The defaults for
the width and size are both unity.
Linestyles created by this mechanism do not replace the default styles;
both may be used.
Not all terminals support the linewidth and pointsize features; if
not supported, the option will be ignored.
Note that this feature is not completely implemented; linestyles defined by
this mechanism may be used with 'plot', 'splot', 'replot', and 'set arrow',
but not by other commands that allow the default index to be used, such as
'set grid'.
Example:
Suppose that the default lines for indices 1, 2, and 3 are red, green, and
blue, respectively, and the default point shapes for the same indices are a
square, a cross, and a triangle, respectively. Then
set linestyle 1 lt 2 lw 2 pt 3 ps 0.5
defines a new linestyle that is green and twice the default width and a new
pointstyle that is a half-sized triangle. The commands
set function style lines
plot f(x) lt 3, g(x) ls 1
will create a plot of f(x) using the default blue line and a plot of g(x)
using the user-defined wide green line. Similarly the commands
set function style linespoints
plot p(x) lt 1 pt 3, q(x) ls 1
will create a plot of f(x) using the default triangles connected by a red
line and q(x) using small triangles connected by a green line.
mapping
If data are provided to splot in spherical or cylindrical coordinates,
the set mapping command should be used to instruct gnuplot how to
interpret them.
Syntax:
set mapping {cartesian | spherical | cylindrical}
A cartesian coordinate system is used by default.
For a spherical coordinate system, the data occupy two or three columns (or
using entries). The first two are interpreted as the polar and azimuthal
angles theta and phi (in the units specified by set angles). The radius r
is taken from the third column if there is one, or is set to unity if there
is no third column. The mapping is:
x = r * cos(theta) * cos(phi)
y = r * sin(theta) * cos(phi)
z = r * sin(phi)
Note that this is a "geographic" spherical system, rather than a "polar" one.
For a cylindrical coordinate system, the data again occupy two or three
columns. The first two are interpreted as theta (in the units specified by
set angles) and z. The radius is either taken from the third column or set
to unity, as in the spherical case. The mapping is:
x = r * cos(theta)
y = r * sin(theta)
z = z
The effects of mapping can be duplicated with the using filter on the
splot command, but mapping may be more convenient if many data files are
to be processed. However even if mapping is used, using may still be
necessary if the data in the file are not in the required order.
mapping has no effect on plot.
Mapping Demos.
multiplot
The command set multiplot places gnuplot in the multiplot mode, in which
several plots are placed on the same page, window, or screen.
Syntax:
set multiplot
set nomultiplot
For some terminals, no plot is displayed until the command set nomultiplot
is given, which causes the entire page to be drawn and then returns gnuplot
to its normal single-plot mode. For other terminals, each separate plot
command produces a plot, but the screen may not be cleared between plots.
Any labels or arrows that have been defined will be drawn for each plot
according to the current size and origin (unless their coordinates are
defined in the screen system). Just about everything else that can be
set is applied to each plot, too. If you want something to appear only
once on the page, for instance a single time stamp, you'll need to put a set
time/set notime pair around one of the plot, splot or replot
commands within the set multiplot/set nomultiplot block.
The commands set origin and set size must be used to correctly position
each plot; see set origin and set size for details of their usage.
Example:
set size 0.7,0.7
set origin 0.1,0.1
set multiplot
set size 0.4,0.4
set origin 0.1,0.1
plot sin(x)
set size 0.2,0.2
set origin 0.5,0.5
plot cos(x)
set nomultiplot
displays a plot of cos(x) stacked above a plot of sin(x). Note the initial
set size and set origin. While these are not always required, their
inclusion is recommended. Some terminal drivers require that bounding box
information be available before any plots can be made, and the form given
above guarantees that the bounding box will include the entire plot array
rather than just the bounding box of the first plot.
set size and set origin refer to the entire plotting area used for each
plot. If you want to have the axes themselves line up, you can guarantee
that the margins are the same size with the set margin commands. See
set margin for their use. Note that the margin settings are absolute,
in character units, so the appearance of the graph in the remaining space
will depend on the screen size of the display device, e.g., perhaps quite
different on a video display and a printer.
See demo.
mxtics
Minor tic marks along the x axis are controlled by set mxtics. They can be
turned off with set nomxtics. Similar commands control minor tics along
the other axes.
Syntax:
set mxtics {<freq> | default}
set nomxtics
show mxtics
The same syntax applies to mytics, mztics, mx2tics and my2tics.
<freq> is the number of sub-intervals (NOT the number of minor tics) between
major tics (ten is the default for a linear axis, so there are nine minor
tics between major tics). Selecting default will return the number of minor
ticks to its default value.
If the axis is logarithmic, the number of sub-intervals will be set to a
reasonable number by default (based upon the length of a decade). This will
be overridden if <freq> is given. However the usual minor tics (2, 3, ...,
8, 9 between 1 and 10, for example) are obtained by setting <freq> to 10,
even though there are but nine sub-intervals.
Minor tics can be used only with uniformly spaced major tics. Since major
tics can be placed arbitrarily by set {x|x2|y|y2|z}tics, minor tics cannot
be used if major tics are explicitly set.
By default, minor tics are off for linear axes and on for logarithmic axes.
They inherit the settings for axis|border and {no}mirror specified for
the major tics. Please see set xtics for information about these.
output
By default, screens are displayed to the standard output. The set output
command redirects the display to the specified file or device.
Syntax:
set output {"<filename>"}
show output
The filename must be enclosed in quotes. If the filename is omitted, any
output file opened by a previous invocation of set output will be closed
and new output will be sent to STDOUT. (If you give the command set output
"STDOUT", your output may be sent to a file named "STDOUT"! ["May be", not
"will be", because some terminals, like x11, ignore set output.])
MSDOS users should note that the \ character has special significance in
double-quoted strings, so single-quotes should be used for filenames in
different directories.
When both set terminal and set output are used together, it is safest to
give set terminal first, because some terminals set a flag which is needed
in some operating systems. This would be the case, for example, if the
operating system needs to know whether or not a file is to be formatted in
order to open it properly.
On machines with popen functions (Unix), output can be piped through a shell
command if the first non-whitespace character of the filename is '|'.
For instance,
set output "|lpr -Plaser filename"
set output "|lp -dlaser filename"
On MSDOS machines, set output "PRN" will direct the output to the default
printer. On VMS, output can be sent directly to any spooled device. It is
also possible to send the output to DECnet transparent tasks, which allows
some flexibility.
parametric
The set parametric command changes the meaning of plot (splot) from
normal functions to parametric functions. The command set noparametric
restores the plotting style to normal, single-valued expression plotting.
Syntax:
set parametric
set noparametric
show parametric
For 2-d plotting, a parametric function is determined by a pair of parametric
functions operating on a parameter. An example of a 2-d parametric function
would be plot sin(t),cos(t), which draws a circle (if the aspect ratio is
set correctly---see set size). gnuplot will display an error message if
both functions are not provided for a parametric plot.
For 3-d plotting, the surface is described as x=f(u,v), y=g(u,v), z=h(u,v).
Therefore a triplet of functions is required. An example of a 3-d parametric
function would be cos(u)*cos(v),cos(u)*sin(v),sin(u), which draws a sphere.
gnuplot will display an error message if all three functions are not
provided for a parametric splot.
The total set of possible plots is a superset of the simple f(x) style plots,
since the two functions can describe the x and y values to be computed
separately. In fact, plots of the type t,f(t) are equivalent to those
produced with f(x) because the x values are computed using the identity
function. Similarly, 3-d plots of the type u,v,f(u,v) are equivalent to
f(x,y).
Note that the order the parametric functions are specified is xfunction,
yfunction (and zfunction) and that each operates over the common parametric
domain.
Also, the set parametric function implies a new range of values. Whereas
the normal f(x) and f(x,y) style plotting assume an xrange and yrange (and
zrange), the parametric mode additionally specifies a trange, urange, and
vrange. These ranges may be set directly with set trange, set urange,
and set vrange, or by specifying the range on the plot or splot
commands. Currently the default range for these parametric variables is
[-5:5]. Setting the ranges to something more meaningful is expected.
polar
The set polar command changes the meaning of the plot from rectangular
coordinates to polar coordinates.
Syntax:
set polar
set nopolar
show polar
There have been changes made to polar mode in version 3.7, so that scripts
for gnuplot versions 3.5 and earlier will require modification. The main
change is that the dummy variable t is used for the angle so that the x and
y ranges can be controlled independently. Other changes are:
1) tics are no longer put along the zero axes automatically
---use set xtics axis nomirror; set ytics axis nomirror;
2) the grid, if selected, is not automatically polar
---use set grid polar;
3) the grid is not labelled with angles
---use set label as necessary.
In polar coordinates, the dummy variable (t) is an angle. The default range
of t is [0:2*pi], or, if degree units have been selected, to [0:360] (see
set angles).
The command set nopolar changes the meaning of the plot back to the default
rectangular coordinate system.
The set polar command is not supported for splots. See the set mapping
command for similar functionality for splots.
While in polar coordinates the meaning of an expression in t is really
r = f(t), where t is an angle of rotation. The trange controls the domain
(the angle) of the function, and the x and y ranges control the range of the
graph in the x and y directions. Each of these ranges, as well as the
rrange, may be autoscaled or set explicitly. See set xrange for details
of all the set range commands.
Example:
set polar
plot t*sin(t)
plot [-2*pi:2*pi] [-3:3] [-3:3] t*sin(t)
The first plot uses the default polar angular domain of 0 to 2*pi. The
radius and the size of the graph are scaled automatically. The second plot
expands the domain, and restricts the size of the graph to [-3:3] in both
directions.
You may want to set size square to have gnuplot try to make the aspect
ratio equal to unity, so that circles look circular.
Polar demos
Polar Data Plot.
size
The set size command scales the displayed size of the plot.
Syntax:
set size {{no}square | ratio <r> | noratio} {<xscale>,<yscale>}
show size
The <xscale> and <yscale> values are the scaling factors for the size of the
plot, which includes the graph and the margins.
ratio causes gnuplot to try to create a graph with an aspect ratio of <r>
(the ratio of the y-axis length to the x-axis length) within the portion of
the plot specified by <xscale> and <yscale>.
The meaning of a negative value for <r> is different. If <r>=-1, gnuplot
tries to set the scales so that the unit has the same length on both the x
and y axes (suitable for geographical data, for instance). If <r>=-2, the
unit on y has twice the length of the unit on x, and so on.
The success of gnuplot in producing the requested aspect ratio depends on
the terminal selected. The graph area will be the largest rectangle of
aspect ratio <r> that will fit into the specified portion of the output
(leaving adequate margins, of course).
square is a synonym for ratio 1.
Both noratio and nosquare return the graph to the default aspect ratio
of the terminal, but do not return <xscale> or <yscale> to their default
values (1.0).
ratio and square have no effect on 3-d plots.
set size is relative to the default size, which differs from terminal to
terminal. Since gnuplot fills as much of the available plotting area as
possible by default, it is safer to use set size to decrease the size of
a plot than to increase it. See set terminal for the default sizes.
On some terminals, changing the size of the plot will result in text being
misplaced.
Examples:
To set the size to normal size use:
set size 1,1
To make the graph half size and square use:
set size square 0.5,0.5
To make the graph twice as high as wide use:
set size ratio 2
See demo.
style
Default styles are chosen with the set function style and set data style
commands. See plot with for information about how to override the default
plotting style for individual functions and data sets.
Syntax:
set function style <style>
set data style <style>
show function style
show data style
The types used for all line and point styles (i.e., solid, dash-dot, color,
etc. for lines; circles, squares, crosses, etc. for points) will be either
those specified on the plot or splot command or will be chosen
sequentially from the types available to the terminal in use. Use the
command test to see what is available.
None of the styles requiring more than two columns of information (e.g.,
errorbars) can be used with splots or function plots. Neither boxes
nor any of the steps styles can be used with splots. If an inappropriate
style is specified, it will be changed to points.
For 2-d data with more than two columns, gnuplot is picky about the allowed
errorbar styles. The using option on the plot command can be used to
set up the correct columns for the style you want. (In this discussion,
"column" will be used to refer both to a column in the data file and an entry
in the using list.)
For three columns, only xerrorbars, yerrorbars (or errorbars), boxes,
and boxerrorbars are allowed. If another plot style is used, the style
will be changed to yerrorbars. The boxerrorbars style will calculate the
boxwidth automatically.
For four columns, only xerrorbars, yerrorbars (or errorbars),
xyerrorbars, boxxyerrorbars, and boxerrorbars are allowed. An illegal
style will be changed to yerrorbars.
Five-column data allow only the boxerrorbars, financebars, and
candlesticks styles. (The last two of these are primarily used for plots
of financial prices.) An illegal style will be changed to boxerrorbars
before plotting.
Six- and seven-column data only allow the xyerrorbars and boxxyerrorbars
styles. Illegal styles will be changed to xyerrorbars before plotting.
For more information about error bars, please see plot errorbars.
boxerrorbars
boxes
boxxyerrorbars
candlesticks
dots
financebars
fsteps
histeps
impulses
lines
linespoints
points
steps
vector
xerrorbars
xyerrorbars
yerrorbars
xyerrorbars
The xyerrorbars style is only relevant to 2-d data plots. xyerrorbars is
like dots, except that horizontal and vertical error bars are also drawn.
At each point (x,y), lines are drawn from (x,y-ydelta) to (x,y+ydelta) and
from (x-xdelta,y) to (x+xdelta,y) or from (x,ylow) to (x,yhigh) and from
(xlow,y) to (xhigh,y), depending upon the number of data columns provided. A
tic mark is placed at the ends of the error bar (unless set bar is
used---see set bar for details).
If data are provided in an unsupported mixed form, the using filter on the
plot command should be used to set up the appropriate form. For example,
if the data are of the form (x,y,xdelta,ylow,yhigh), then you can use
plot 'data' using 1:2:($1-$3),($1+$3),4,5 with xyerrorbars
atari ST (via VDI)
The vdi terminal is the same as the atari terminal, except that it sends
output to the screen via the VDI and not into AES-Windows.
The vdi terminal has options to set the character size and the screen
colors.
Syntax:
set terminal vdi {<fontsize>} {<col0> <col1> ... <col15.}
The character size must appear if any colors are to be specified. Each of
the (up to 16) colors is given as a three-digit hex number, where the digits
represent RED, GREEN and BLUE (in that order). The range of 0--15 is scaled
to whatever color range the screen actually has. On a normal ST screen, odd
and even intensities are the same.
Examples:
set terminal vdi 4 # use small (6x6) font
set terminal vdi 6 0 # set monochrome screen to white on black
set terminal vdi 13 0 fff f00 f0 f ff f0f
# set first seven colors to black, white, green, blue,
# cyan, purple, and yellow and use large font (8x16).
Additionally, if an environment variable GNUCOLORS exists, its contents are
interpreted as an options string, but an explicit terminal option takes
precedence.
be
gnuplot provides the be terminal type for use with X servers. This
terminal type is set automatically at startup if the DISPLAY environment
variable is set, if the TERM environment variable is set to xterm, or
if the -display command line option is used.
Syntax:
set terminal be {reset} {<n>}
Multiple plot windows are supported: set terminal be <n> directs the
output to plot window number n. If n>0, the terminal number will be
appended to the window title and the icon will be labeled gplt <n>.
The active window may distinguished by a change in cursor (from default
to crosshair.)
Plot windows remain open even when the gnuplot driver is changed to a
different device. A plot window can be closed by pressing the letter q
while that window has input focus, or by choosing close from a window
manager menu. All plot windows can be closed by specifying reset, which
actually terminates the subprocess which maintains the windows (unless
-persist was specified).
Plot windows will automatically be closed at the end of the session
unless the -persist option was given.
The size or aspect ratio of a plot may be changed by resizing the gnuplot
window.
Linewidths and pointsizes may be changed from within gnuplot with
set linestyle.
For terminal type be, gnuplot accepts (when initialized) the standard
X Toolkit options and resources such as geometry, font, and name from the
command line arguments or a configuration file. See the X(1) man page
(or its equivalent) for a description of such options.
A number of other gnuplot options are available for the be terminal.
These may be specified either as command-line options when gnuplot is
invoked or as resources in the configuration file "/.Xdefaults". They are
set upon initialization and cannot be altered during a gnuplot session.
command-line_options
monochome_options
color_resources
grayscale_resources
line_resources
cgm
The cgm terminal generates a Computer Graphics Metafile, Version 1.
This file format is a subset of the ANSI X3.122-1986 standard entitled
"Computer Graphics - Metafile for the Storage and Transfer of Picture
Description Information".
Several options may be set in cgm.
Syntax:
set terminal cgm {<mode>} {<color>} {<rotation>} {solid | dashed}
{width <plot_width>} {linewidth <line_width>}
{"<font>"} {<fontsize>}
{<color0> <color1> <color2> ...}
where <mode> is landscape, portrait, or default;
<color> is either color or monochrome;
<rotation> is either rotate or norotate;
solid draws all curves with solid lines, overriding any dashed patterns;
<plot_width> is the assumed width of the plot in points;
<line_width> is the line width in points (default 1);
<font> is the name of a font; and
<fontsize> is the size of the font in points (default 12).
By default, cgm uses rotated text for the Y axis label.
The first six options can be in any order. Selecting default sets all
options to their default values.
Each color must be of the form 'xrrggbb', where x is the literal
character 'x' and 'rrggbb' are the red, green and blue components in
hex. For example, 'x00ff00' is green. The background color is set
first, then the plotting colors.
Examples:
set terminal cgm landscape color rotate dashed width 432 \
linewidth 1 'Helvetica Bold' 12 # defaults
set terminal cgm 14 linewidth 2 14 # wider lines & larger font
set terminal cgm portrait "Times Italic" 12
set terminal cgm color solid # no pesky dashes!
font
linewidth
rotate
solid
size
width
nofontlist
font
The first part of a Computer Graphics Metafile, the metafile description,
includes a font table. In the picture body, a font is designated by an
index into this table. By default, this terminal generates a table with
the following 16 fonts, plus six more with italic replaced by
oblique, or vice-versa (since at least the Microsoft Office and Corel
Draw CGM import filters treat italic and oblique as equivalent):
Helvetica
Helvetica Bold
Helvetica Oblique
Helvetica Bold Oblique
Times Roman
Times Bold
Times Italic
Times Bold Italic
Courier
Courier Bold
Courier Oblique
Courier Bold Oblique
Symbol
Hershey/Cartographic_Roman
Hershey/Cartographic_Greek
Hershey/Simplex_Roman
Hershey/Simplex_Greek
Hershey/Simplex_Script
Hershey/Complex_Roman
Hershey/Complex_Greek
Hershey/Complex_Script
Hershey/Complex_Italic
Hershey/Complex_Cyrillic
Hershey/Duplex_Roman
Hershey/Triplex_Roman
Hershey/Triplex_Italic
Hershey/Gothic_German
Hershey/Gothic_English
Hershey/Gothic_Italian
Hershey/Symbol_Set_1
Hershey/Symbol_Set_2
Hershey/Symbol_Math
ZapfDingbats
Script
15
The first thirteen of these fonts are required for WebCGM. The
Microsoft Office CGM import filter implements the 13 standard fonts
listed above, and also 'ZapfDingbats' and 'Script'. However, the
script font may only be accessed under the name '15'. For more on
Microsoft import filter font substitutions, check its help file which
you may find here:
C:\Program Files\Microsoft Office\Office\Cgmimp32.hlp
and/or its configuration file, which you may find here:
C:\Program Files\Common Files\Microsoft Shared\Grphflt\Cgmimp32.cfg
In the set term command, you may specify a font name which does not
appear in the default font table. In that case, a new font table is
constructed with the specified font as its first entry. You must ensure
that the spelling, capitalization, and spacing of the name are
appropriate for the application that will read the CGM file. (Gnuplot
and any MIL-D-28003A compliant application ignore case in font names.)
If you need to add several new fonts, use several set term commands.
Example:
set terminal cgm 'Old English'
set terminal cgm 'Tengwar'
set terminal cgm 'Arabic'
set output 'myfile.cgm'
plot ...
set output
You cannot introduce a new font in a set label command.2 fontsize
Fonts are scaled assuming the page is 6 inches wide. If the size
command is used to change the aspect ratio of the page or the CGM file
is converted to a different width, the resulting font sizes will be
scaled up or down accordingly. To change the assumed width, use the
width option.
eepic
The eepic terminal driver supports the extended LaTeX picture environment.
It is an alternative to the latex driver.
The output of this terminal is intended for use with the "eepic.sty" macro
package for LaTeX. To use it, you need "eepic.sty", "epic.sty" and a
printer driver that supports the "tpic" \specials. If your printer driver
doesn't support those \specials, "eepicemu.sty" will enable you to use some
of them.
dvips and dvipdfm do support the "tpic" \specials.
Syntax:
set terminal eepic {color, dashed, rotate, small, tiny, default, <fontsize>}
Options:
You can give options in any order you wish.
'color' causes gnuplot to produce \color{...} commands so that the graphs are
colored. Using this option, you must include \usepackage{color} in the preambel
of your latex document.
'dashed' will allow dashed line types; without this option, only solid lines
with varying thickness will be used.
'dashed' and 'color' are mutually exclusive; if 'color' is specified, then 'dashed'
will be ignored
'rotate' will enable true rotated text (by 90 degrees). Otherwise, rotated text
will be typeset with letters stacked above each other. If you use this option
you must include \usepackage{graphicx} in the preamble.
'small' will use \scriptsize symbols as point markers (Probably does not work
with TeX, only LaTeX2e). Default is to use the default math size.
'tiny' uses \scriptscriptstyle symbols.
'default' resets all options to their defaults = no color, no dashed lines,
pseudo-rotated (stacked) text, large point symbols.
<fontsize> is a number which specifies the font size inside the picture
environment; the unit is pt (points), i.e., 10 pt equals approx. 3.5 mm.
If fontsize is not specified, then all text inside the picture will be set
in \footnotesize.
Notes:
Remember to escape the # character (or other chars meaningful to (La-)TeX)
by \\ (2 backslashes).
It seems that dashed lines become solid lines when the vertices of a plot
are too close. (I do not know if that is a general problem with the tpic specials,
or if it is caused by a bug in eepic.sty or dvips/dvipdfm.)
The default size of an eepic plot is 5x3 inches, which can be scaled
by 'set size a,b'
Points, among other things, are drawn using the LaTeX commands "\Diamond",
"\Box", etc. These commands no longer belong to the LaTeX2e core; they are
included in the latexsym package, which is part of the base distribution and
thus part of any LaTeX implementation. Please do not forget to use this package.
Instead of latexsym, you can also include the amssymb package. All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '{', you also need to include a '}' at the
end of the text, and the whole text will be centered both horizontally and
vertically. If the text string begins with '[', you need to follow this with
a position specification (up to two out of t,b,l,r), ']{', the text itself,
and finally '}'. The text itself may be anything LaTeX can typeset as an
LR-box. '\rule{}{}'s may help for best positioning.
Examples:
set term eepic
output graphs as eepic macros inside a picture environment;
\input the resulting file in your LaTeX document.
set term eepic color tiny rotate 8
eepic macros with \color macros, \scripscriptsize point markers,
true rotated text, and all text set with 8pt.
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
set title '\LaTeX\ -- $ \gamma $'
Force centering both horizontally and vertically:
set label '{\LaTeX\ -- $ \gamma $}' at 0,0
Specify own positioning (top here):
set xlabel '[t]{\LaTeX\ -- $ \gamma $}'
The other label -- account for long ticlabels:
set ylabel '[r]{\LaTeX\ -- $ \gamma $\rule{7mm}{0pt}'
epslatex
Two options may be set in the epslatex driver.
Syntax:
set terminal epslatex {default}
{color | monochrome} {solid | dashed}
{"<fontname>"} {<fontsize>}
default mode sets all options to their defaults: monochrome, dashed,
"default" and 11pt.
Default size of a plot is 5 inches wide and 3 inches high.
solid draws all plots with solid lines, overriding any dashed patterns;
"<fontname>" is the name of font; and <fontsize> is
the size of the font in PostScript points. Font selection isn't supported yet.
Font size selection is supported only for the calculation of proper spacing.
The actual LaTeX font at the point of inclusion is taken, so use LaTeX commands
for changing fonts. If you use e.g. 12pt as font size for your LaTeX documents,
use '"default" 12' as options.
All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '{', you also need to include a '}' at the
end of the text, and the whole text will be centered both horizontally
and vertically by LaTeX. --- If the text string begins with '[', you need
to continue it with: a position specification (up to two out of t,b,l,r),
']{', the text itself, and finally, '}'. The text itself may be anything
LaTeX can typeset as an LR-box. \rule{}{}'s may help for best positioning.
See also the documenation of the pslatex terminal driver.
To create multiline labels, use \shortstack, example
set ylabel '[r]{\shortstack{first line \\ second line}}'
The driver produces two different files, one for the LaTeX part and one for
the eps part of the figure.
The name of the LaTeX file is derived from the name of
the eps file given on the set output command; it is determined by replacing
the trailing .eps (actually just the final extent in the file name---and
the option will be turned off if there is no extent) with .tex in the output
file name. Remember to close the file before leaving gnuplot.
There is no LaTeX output if no output file is given!
In your LaTeX documents use '\input{filename}' for inclusion of the figure.
Include \usepackage{graphics} in the preambel!
Via 'epstopdf' (contained e.g. in the teTeX package, requires ghostscript)
pdf files can made out of the eps files. If the graphics package is properly
configured, the LaTeX files can also be processed by pdflatex without
changes, and the pdf files are included instead of the eps files
epson-180dpi
This driver supports a family of Epson printers and derivatives.
epson-180dpi and epson-60dpi are drivers for Epson LQ-style 24-pin
printers with resolutions of 180 and 60 dots per inch, respectively.
epson-lx800 is a generic 9-pin driver appropriate for printers like the
Epson LX-800, the Star NL-10 and NX-1000, the PROPRINTER, and so forth.
nec-cp6 is generix 24-pin driver that can be used for printers like the
NEC CP6 and the Epson LQ-800.
The okidata driver supports the 9-pin OKIDATA 320/321 Standard printers.
The starc driver is for the Star Color Printer.
The tandy-60dpi driver is for the Tandy DMP-130 series of 9-pin, 60-dpi
printers.
Only nec-cp6 has any options.
Syntax:
set terminal nec-cp6 {monochrome | colour | draft}
which defaults to monochrome.
With each of these drivers, a binary copy is required on a PC to print. Do
not use print---use instead copy file /b lpt1:.
fig
The fig terminal device generates output in the Fig graphics language.
Syntax:
set terminal fig {monochrome | color} {small | big}
{pointsmax <max_points>}
{landscape | portrait}
{metric | inches}
{fontsize <fsize>}
{size <xsize> <ysize>}
{thickness <units>}
{depth <layer>}
monochrome and color determine whether the picture is black-and-white or
color. small and big produce a 5x3 or 8x5 inch graph in the default
landscape mode and 3x5 or 5x8 inches in portrait mode. <max_points>
sets the maximum number of points per polyline. Default units for editing
with "xfig" may be metric or inches. fontsize sets the size of the
text font to <fsize> points. size sets (overrides) the size of the drawing
area to <xsize>*<ysize> in units of inches or centimeters depending on the
inches or metric setting in effect. depth sets the default depth layer
for all lines and text. The default depth is 10 to leave room for adding
material with "xfig" on top of the plot.
thickness sets the default line thickness, which is 1 if not specified.
Overriding the thickness can be achieved by adding a multiple of 100 to the
to the linetype value for a plot command. In a similar way the depth
of plot elements (with respect to the default depth) can be controlled by
adding a multiple of 1000 to <linetype>. The depth is then <layer> +
<linetype>/1000 and the thickness is (<linetype>%1000)/100 or, if that is
zero, the default line thickness.
Additional point-plot symbols are also available with the fig driver. The
symbols can be used through pointtype values % 100 above 50, with different
fill intensities controlled by <pointtype> % 5 and outlines in black (for
<pointtype> % 10 < 5) or in the current color. Available symbols are
50 - 59: circles
60 - 69: squares
70 - 79: diamonds
80 - 89: upwards triangles
90 - 99: downwards triangles
The size of these symbols is linked to the font size. The depth of symbols
is by default one less than the depth for lines to achieve nice error bars.
If <pointtype> is above 1000, the depth is <layer> + <pointtype>/1000-1. If
<pointtype>%1000 is above 100, the fill color is (<pointtype>%1000)/100-1.
Available fill colors are (from 1 to 9): black, blue, green, cyan, red,
magenta, yellow, white and dark blue (in monochrome mode: black for 1 to 6
and white for 7 to 9).
See plot with for details of <linetype> and <pointtype>.
The big option is a substitute for the bfig terminal in earlier versions,
which is no longer supported.
Examples:
set terminal fig monochrome small pointsmax 1000 # defaults
plot 'file.dat' with points linetype 102 pointtype 759
would produce circles with a blue outline of width 1 and yellow fill color.
plot 'file.dat' using 1:2:3 with err linetype 1 pointtype 554
would produce errorbars with black lines and circles filled red. These
circles are one layer above the lines (at depth 9 by default).
To plot the error bars on top of the circles use
plot 'file.dat' using 1:2:3 with err linetype 1 pointtype 2554
gif
The gif terminal driver generates output in GIF format. It uses Thomas
Boutell's gd library, which is available from http://www.boutell.com/gd/
By default, the gif terminal driver uses a shared Web-friendy palette.
Syntax:
set terminal gif {transparent} {interlace}
{tiny | small | medium | large | giant}
{size <x>,<y>}
{<color0> <color1> <color2> ...}
transparent instructs the driver to generate transparent GIFs. The first
color will be the transparent one.
interlace instructs the driver to generate interlaced GIFs.
The choice of fonts is tiny (5x8 pixels), small (6x12 pixels), medium
(7x13 Bold), large (8x16) or giant (9x15 pixels)
The size <x,y> is given in pixels---it defaults to 640x480. The number of
pixels can be also modified by scaling with the set size command.
Each color must be of the form 'xrrggbb', where x is the literal character
'x' and 'rrggbb' are the red, green and blue components in hex. For example,
'x00ff00' is green. The background color is set first, then the border
colors, then the X & Y axis colors, then the plotting colors. The maximum
number of colors that can be set is 256.
Examples:
set terminal gif small size 640,480 \
xffffff x000000 x404040 \
xff0000 xffa500 x66cdaa xcdb5cd \
xadd8e6 x0000ff xdda0dd x9500d3 # defaults
which uses white for the non-transparent background, black for borders, gray
for the axes, and red, orange, medium aquamarine, thistle 3, light blue, blue,
plum and dark violet for eight plotting colors.
set terminal gif transparent xffffff \
x000000 x202020 x404040 x606060 \
x808080 xA0A0A0 xC0C0C0 xE0E0E0 \
which uses white for the transparent background, black for borders, dark
gray for axes, and a gray-scale for the six plotting colors.
The page size is 640x480 pixels. The gif driver can create either color
or monochromatic output, but you have no control over which is produced.
The current version of the gif driver does not support animated GIFs.
gpic
The gpic terminal driver generates GPIC graphs in the Free Software
Foundations's "groff" package. The default size is 5 x 3 inches. The only
option is the origin, which defaults to (0,0).
Syntax:
set terminal gpic {<x> <y>}
where x and y are in inches.
A simple graph can be formatted using
groff -p -mpic -Tps file.pic > file.ps.
The output from pic can be pipe-lined into eqn, so it is possible to put
complex functions in a graph with the set label and set {x/y}label
commands. For instance,
set ylab '@space 0 int from 0 to x alpha ( t ) roman d t@'
will label the y axis with a nice integral if formatted with the command:
gpic filename.pic | geqn -d@@ -Tps | groff -m[macro-package] -Tps
> filename.ps
Figures made this way can be scaled to fit into a document. The pic language
is easy to understand, so the graphs can be edited by hand if need be. All
co-ordinates in the pic-file produced by gnuplot are given as x+gnuplotx
and y+gnuploty. By default x and y are given the value 0. If this line is
removed with an editor in a number of files, one can put several graphs in
one figure like this (default size is 5.0x3.0 inches):
.PS 8.0
x=0;y=3
copy "figa.pic"
x=5;y=3
copy "figb.pic"
x=0;y=0
copy "figc.pic"
x=5;y=0
copy "figd.pic"
.PE
This will produce an 8-inch-wide figure with four graphs in two rows on top
of each other.
One can also achieve the same thing by the command
set terminal gpic x y
for example, using
.PS 6.0
copy "trig.pic"
.PE
hpgl
The hpgl driver produces HPGL output for devices like the HP7475A plotter.
There are two options which can be set: the number of pens and eject,
which tells the plotter to eject a page when done. The default is to use 6
pens and not to eject the page when done.
The international character sets ISO-8859-1 and CP850 are recognized via
set encoding iso_8859_1 or set encoding cp850 (see set encoding for
details).
Syntax:
set terminal hpgl {<number_of_pens>} {eject}
The selection
set terminal hpgl 8 eject
is equivalent to the previous hp7550 terminal, and the selection
set terminal hpgl 4
is equivalent to the previous hp7580b terminal.
The pcl5 driver supports plotters such as the Hewlett-Packard Designjet
750C, the Hewlett-Packard Laserjet III, and the Hewlett-Packard Laserjet IV.
It actually uses HPGL-2, but there is a name conflict among the terminal
devices. It has several options which must be specified in the order
indicated below:
Syntax:
set terminal pcl5 {mode <mode>} {<plotsize>}
{{color {<number_of_pens>}} | monochrome} {solid | dashed}
{font <font>} {size <fontsize>} {pspoints | nopspoints}
<mode> is landscape or portrait. <plotsize> is the physical
plotting size of the plot, which is one of the following: letter for
standard (8 1/2" X 11") displays, legal for (8 1/2" X 14") displays,
noextended for (36" X 48") displays (a letter size ratio) or,
extended for (36" X 55") displays (almost a legal size ratio).
color is for multi-pen (i.e. color) plots, and <number_of_pens> is
the number of pens (i.e. colors) used in color plots. monochrome is for
one (e.g. black) pen plots. solid draws all lines as solid lines, or
'dashed' will draw lines with different dashed and dotted line patterns.
<font> is stick, univers, cg_times, zapf_dingbats, antique_olive,
arial, courier, garamond_antigua, letter_gothic, cg_omega,
albertus, times_new_roman, clarendon, coronet, marigold,
truetype_symbols, or wingdings. <fontsize> is the font size in points.
The point type selection can be the standard default set by specifying
nopspoints, or the same set of point types found in the postscript terminal
by specifying pspoints.
Note that built-in support of some of these options is printer device
dependendent. For instance, all the fonts are supposedly supported by the HP
Laserjet IV, but only a few (e.g. univers, stick) may be supported by the HP
Laserjet III and the Designjet 750C. Also, color obviously won't work on the
the laserjets since they are monochrome devices.
Defaults: landscape, noextended, color (6 pens), solid, univers, 12 point,
and nopspoints.
With pcl5 international characters are handled by the printer; you just put
the appropriate 8-bit character codes into the text strings. You don't need
to bother with set encoding.
HPGL graphics can be imported by many software packages.
latex
The latex and emtex drivers allow two options.
Syntax:
set terminal latex | emtex {courier | roman | default} {<fontsize>}
fontsize may be any size you specify. The default is for the plot to
inherit its font setting from the embedding document.
Unless your driver is capable of building fonts at any size (e.g. dvips),
stick to the standard 10, 11 and 12 point sizes.
METAFONT users beware: METAFONT does not like odd sizes.
All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '{', you also need to include a '}' at the
end of the text, and the whole text will be centered both horizontally and
vertically. If the text string begins with '[', you need to follow this with
a position specification (up to two out of t,b,l,r), ']{', the text itself,
and finally '}'. The text itself may be anything LaTeX can typeset as an
LR-box. '\rule{}{}'s may help for best positioning.
Points, among other things, are drawn using the LaTeX commands "\Diamond" and
"\Box". These commands no longer belong to the LaTeX2e core; they are included
in the latexsym package, which is part of the base distribution and thus part
of any LaTeX implementation. Please do not forget to use this package.
Points are drawn with the LaTex commands \Diamond and \Box. These
commands do no longer belong to the LaTeX2e core, but are included in the
latexsym-package in the base distribution, and are hence part of all LaTeX
implementations. Please do not forget to use this package.
Examples:
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
set title '\LaTeX\ -- $ \gamma $'
Force centering both horizontally and vertically:
set label '{\LaTeX\ -- $ \gamma $}' at 0,0
Specify own positioning (top here):
set xlabel '[t]{\LaTeX\ -- $ \gamma $}'
The other label -- account for long ticlabels:
set ylabel '[r]{\LaTeX\ -- $ \gamma $\rule{7mm}{0pt}'
macintosh
Several options may be set in the 'macintosh' driver.
Syntax:
set terminal macintosh {singlewin | multiwin} {vertical | novertical}
{size <width>, <height> | default}
'singlewin' limits the output to a single window and is useful for animations.
'multiwin' allows multiple windows.
'vertical' is only valid under the gx option. With this option, rotated text
be drawn vertically. novertical turns this option off.
size <width>, <height> overrides the graph size set in the preferences
dialog until it is cleared with either 'set term mac size default'
or 'set term mac default'.
'set term mac size default' sets the window size settings to those set in
the preferences dialog.
'set term mac default' sets all options to their default values.
Default values: nogx, multiwin, novertical.
If you generate graphs under the multiwin option and then switch to singlewin,
the next plot command will cause one more window to be created. This new
window will be reused as long as singlewin is in effect. If you switch back
to multiwin, generate some graphs, and then switch to singlewin again, the
orginal 'singlewin' window will be resused if it is still open. Otherwise
a new 'singlewin' window will be created. The 'singlewin' window is not numbered.
METAFONT Instructions
- Set your terminal to METAFONT:
set terminal mf
- Select an output-file, e.g.:
set output "myfigures.mf"
- Create your pictures. Each picture will generate a separate character. Its
default size will be 5*3 inches. You can change the size by saying set size
0.5,0.5 or whatever fraction of the default size you want to have.
- Quit gnuplot.
- Generate a TFM and GF file by running METAFONT on the output of gnuplot.
Since the picture is quite large (5*3 in), you will have to use a version of
METAFONT that has a value of at least 150000 for memmax. On Unix systems
these are conventionally installed under the name bigmf. For the following
assume that the command virmf stands for a big version of METAFONT. For
example:
- Invoke METAFONT:
virmf '&plain'
- Select the output device: At the METAFONT prompt ('*') type:
\mode:=CanonCX; % or whatever printer you use
- Optionally select a magnification:
mag:=1; % or whatever you wish
- Input the gnuplot-file:
input myfigures.mf
On a typical Unix machine there will usually be a script called "mf" that
executes virmf '&plain', so you probably can substitute mf for virmf &plain.
This will generate two files: mfput.tfm and mfput.$$$gf (where $$$ indicates
the resolution of your device). The above can be conveniently achieved by
typing everything on the command line, e.g.:
virmf '&plain' '\mode:=CanonCX; mag:=1; input myfigures.mf'
In this case the output files will be named myfigures.tfm and
myfigures.300gf.
- Generate a PK file from the GF file using gftopk:
gftopk myfigures.300gf myfigures.300pk
The name of the output file for gftopk depends on the DVI driver you use.
Ask your local TeX administrator about the naming conventions. Next, either
install the TFM and PK files in the appropriate directories, or set your
environment variables properly. Usually this involves setting TEXFONTS to
include the current directory and doing the same thing for the environment
variable that your DVI driver uses (no standard name here...). This step is
necessary so that TeX will find the font metric file and your DVI driver will
find the PK file.
- To include your pictures in your document you have to tell TeX the font:
\font\gnufigs=myfigures
Each picture you made is stored in a single character. The first picture is
character 0, the second is character 1, and so on... After doing the above
step, you can use the pictures just like any other characters. Therefore, to
place pictures 1 and 2 centered in your document, all you have to do is:
\centerline{\gnufigs\char0}
\centerline{\gnufigs\char1}
in plain TeX. For LaTeX you can, of course, use the picture environment and
place the picture wherever you wish by using the \makebox and \put macros.
This conversion saves you a lot of time once you have generated the font;
TeX handles the pictures as characters and uses minimal time to place them,
and the documents you make change more often than the pictures do. It also
saves a lot of TeX memory. One last advantage of using the METAFONT driver
is that the DVI file really remains device independent, because no \special
commands are used as in the eepic and tpic drivers.
mp
The mp driver produces output intended to be input to the Metapost program.
Running Metapost on the file creates EPS files containing the plots. By
default, Metapost passes all text through TeX. This has the advantage of
allowing essentially any TeX symbols in titles and labels.
The mp terminal is selected with a command of the form
set term mp {color} {solid} {notex} {mag <magsize>} {"<name>"} {<size>}
The option color causes lines to be drawn in color (on a printer or display
that supports it), monochrome (or nothing) selects black lines. The option
solid draws solid lines, while dashed (or nothing) selects lines with
different patterns of dashes. If solid is selected but color is not,
nearly all lines will be identical. This may occasionally be useful, so it is
allowed.
The option notex bypasses TeX entirely, therefore no TeX code can be used in
labels under this option. This is intended for use on old plot files or files
that make frequent use of common characters like $ and % that require
special handling in TeX.
Changing font sizes in TeX has no effect on the size of mathematics, and there
is no foolproof way to make such a change, except by globally setting a
magnification factor. This is the purpose of the magnification option. It
must be followed by a scaling factor. All text (NOT the graphs) will be scaled
by this factor. Use this if you have math that you want at some size other
than the default 10pt. Unfortunately, all math will be the same size, but see
the discussion below on editing the MP output. mag will also work under
notex but there seems no point in using it as the font size option (below)
works as well.
A name in quotes selects the font that will be used when no explicit font is
given in a set label or set title. A name recognized by TeX (a TFM file
exists) must be used. The default is "cmr10" unless notex is selected,
then it is "pcrr8r" (Courier). Even under notex, a TFM file is needed by
Metapost. The file pcrr8r.tfm is the name given to Courier in LaTeX's psnfss
package. If you change the font from the notex default, choose a font that
matches the ASCII encoding at least in the range 32-126. cmtt10 almost
works, but it has a nonblank character in position 32 (space).
The size can be any number between 5.0 and 99.99. If it is omitted, 10.0 is
used. It is advisable to use magstep sizes: 10 times an integer or
half-integer power of 1.2, rounded to two decimals, because those are the most
available sizes of fonts in TeX systems.
All the options are optional. If font information is given, it must be at the
end, with size (if present) last. The size is needed to select a size for the
font, even if the font name includes size information. For example,
set term mp "cmtt12" selects cmtt12 shrunk to the default size 10. This
is probably not what you want or you would have used cmtt10.
The following common ascii characters need special treatment in TeX:
$, &, #, %, _; |, <, >; ^, ~, \, {, and }
The five characters $, #, &, _, and % can simply be escaped, e.g., \$.
The three characters <, >, and | can be wrapped in math mode, e.g., $<$.
The remainder require some TeX work-arounds. Any good book on TeX will give
some guidance.
If you type your labels inside double quotes, backslashes in TeX code need to
be escaped (doubled). Using single quotes will avoid having to do this, but
then you cannot use \n for line breaks. As of this writing, version 3.7 of
gnuplot processess titles given in a plot command differently than in other
places, and backslashes in TeX commands need to be doubled regardless of the
style of quotes.
Metapost pictures are typically used in TeX documents. Metapost deals with
fonts pretty much the same way TeX does, which is different from most other
document preparation programs. If the picture is included in a LaTeX document
using the graphics package, or in a plainTeX document via epsf.tex, and then
converted to PostScript with dvips (or other dvi-to-ps converter), the text in
the plot will usually be handled correctly. However, the text may not appear
if you send the Metapost output as-is to a PostScript interpreter.
Metapost Instructions
Metapost Instructions
- Set your terminal to Metapost, e.g.:
set terminal mp mono "cmtt12" 12
- Select an output-file, e.g.:
set output "figure.mp"
- Create your pictures. Each plot (or multiplot group) will generate a
separate Metapost beginfig...endfig group. Its default size will be 5 by 3
inches. You can change the size by saying set size 0.5,0.5 or whatever
fraction of the default size you want to have.
- Quit gnuplot.
- Generate EPS files by running Metapost on the output of gnuplot:
mpost figure.mp OR mp figure.mp
The name of the Metapost program depends on the system, typically mpost for
a Unix machine and mp on many others. Metapost will generate one EPS file
for each picture.
- To include your pictures in your document you can use the graphics package
in LaTeX or epsf.tex in plainTeX:
\usepackage{graphics} % LaTeX
\input epsf.tex % plainTeX
If you use a driver other than dvips for converting TeX DVI output to PS, you
may need to add the following line in your LaTeX document:
\DeclareGraphicsRule{*}{eps}{*}{}
Each picture you made is in a separate file. The first picture is in, e.g.,
figure.0, the second in figure.1, and so on.... To place the third picture in
your document, for example, all you have to do is:
\includegraphics{figure.2} % LaTeX
\epsfbox{figure.2} % plainTeX
The advantage, if any, of the mp terminal over a postscript terminal is
editable output. Considerable effort went into making this output as clean as
possible. For those knowledgeable in the Metapost language, the default line
types and colors can be changed by editing the arrays lt[] and col[].
The choice of solid vs dashed lines, and color vs black lines can be change by
changing the values assigned to the booleans dashedlines and colorlines.
If the default tex option was in effect, global changes to the text of
labels can be achieved by editing the vebatimtex...etex block. In
particular, a LaTeX preamble can be added if desired, and then LaTeX's
built-in size changing commands can be used for maximum flexibility. Be sure
to set the appropriate MP configuration variable to force Metapost to run
LaTeX instead of plainTeX.
pbm
Several options may be set in the pbm terminal---the driver for PBMplus.
Syntax:
set terminal pbm {<fontsize>} {<mode>}
where <fontsize> is small, medium, or large and <mode> is monochrome,
gray or color. The default plot size is 640 pixels wide and 480 pixels
high; this may be changed by set size.
The output of the pbm driver depends upon <mode>: monochrome produces a
portable bitmap (one bit per pixel), gray a portable graymap (three bits
per pixel) and color a portable pixmap (color, four bits per pixel).
The output of this driver can be used with Jef Poskanzer's excellent PBMPLUS
package, which provides programs to convert the above PBMPLUS formats to GIF,
TIFF, MacPaint, Macintosh PICT, PCX, X11 bitmap and many others. PBMPLUS may
be obtained from ftp.x.org. The relevant files have names that begin with
"netpbm-1mar1994.p1"; they reside in /contrib/utilities. The package can
probably also be obtained from one of the many sites that mirrors ftp.x.org.
Examples:
set terminal pbm small monochrome # defaults
set size 2,2; set terminal pbm color medium
postscript
Several options may be set in the postscript driver.
Syntax:
set terminal postscript {<mode>} {enhanced | noenhanced}
{color | monochrome} {solid | dashed}
{<duplexing>}
{"<fontname>"} {<fontsize>}
where <mode> is landscape, portrait, eps or default;
solid draws all plots with solid lines, overriding any dashed patterns;
<duplexing> is defaultplex, simplex or duplex ("duplexing" in
PostScript is the ability of the printer to print on both sides of the same
page---don't set this if your printer can't do it);
enhanced activates the "enhanced PostScript" features (subscripts,
superscripts and mixed fonts);
"<fontname>" is the name of a valid PostScript font; and <fontsize> is
the size of the font in PostScript points.
default mode sets all options to their defaults: landscape, monochrome,
dashed, defaultplex, noenhanced, "Helvetica" and 14pt.
Default size of a PostScript plot is 10 inches wide and 7 inches high.
eps mode generates EPS (Encapsulated PostScript) output, which is just
regular PostScript with some additional lines that allow the file to be
imported into a variety of other applications. (The added lines are
PostScript comment lines, so the file may still be printed by itself.) To
get EPS output, use the eps mode and make only one plot per file. In eps
mode the whole plot, including the fonts, is reduced to half of the default
size.
Examples:
set terminal postscript default # old postscript
set terminal postscript enhanced # old enhpost
set terminal postscript landscape 22 # old psbig
set terminal postscript eps 14 # old epsf1
set terminal postscript eps 22 # old epsf2
set size 0.7,1.4; set term post portrait color "Times-Roman" 14
Linewidths and pointsizes may be changed with set linestyle.
The postscript driver supports about 70 distinct pointtypes, selectable
through the pointtype option on plot and set linestyle.
Several possibly useful files about gnuplot's PostScript are included
in the /docs/ps subdirectory of the gnuplot distribution and at the
distribution sites. These are "ps_symbols.gpi" (a gnuplot command file
that, when executed, creates the file "ps_symbols.ps" which shows all the
symbols available through the postscript terminal), "ps_guide.ps" (a
PostScript file that contains a summary of the enhanced syntax and a page
showing what the octal codes produce with text and symbol fonts) and
"ps_file.doc" (a text file that contains a discussion of the organization
of a PostScript file written by gnuplot).
A PostScript file is editable, so once gnuplot has created one, you are
free to modify it to your heart's desire. See the "editing postscript"
section for some hints.
enhanced postscript
editing postscript
enhanced postscript
Control Examples Explanation
^ a^x superscript
_ a_x subscript
@ @x or a@^b_c phantom box (occupies no width)
& &{space} inserts space of specified length
Braces can be used to place multiple-character text where a single character
is expected (e.g., 2^{10}). To change the font and/or size, use the full
form: {/[fontname][=fontsize | *fontscale] text}. Thus {/Symbol=20 G} is a
20-point GAMMA) and {/*0.75 K} is a K at three-quarters of whatever fontsize
is currently in effect. (The '/' character MUST be the first character after
the '{'.)
If the encoding vector has been changed by set encoding, the default
encoding vector can be used instead by following the slash with a dash. This
is unnecessary if you use the Symbol font, however---since /Symbol uses its
own encoding vector, gnuplot will not apply any other encoding vector to
it.
The phantom box is useful for a@^b_c to align superscripts and subscripts
but does not work well for overwriting an accent on a letter. (To do the
latter, it is much better to use set encoding iso_8859_1 to change to the
ISO Latin-1 encoding vector, which contains a large variety of letters with
accents or other diacritical marks.) Since the box is non-spacing, it is
sensible to put the shorter of the subscript or superscript in the box (that
is, after the @).
Space equal in length to a string can be inserted using the '&' character.
Thus
'abc&{def}ghi'
would produce
'abc ghi'.
You can access special symbols numerically by specifying \character-code (in
octal), e.g., {/Symbol \245} is the symbol for infinity.
You can escape control characters using \, e.g., \\, \{, and so on.
But be aware that strings in double-quotes are parsed differently than those
enclosed in single-quotes. The major difference is that backslashes may need
to be doubled when in double-quoted strings.
Examples (these are hard to describe in words---try them!):
set xlabel 'Time (10^6 {/Symbol m}s)'
set title '{/Symbol=18 \362@_{/=9.6 0}^{/=12 x}} \
{/Helvetica e^{-{/Symbol m}^2/2} d}{/Symbol m}'
The file "ps_guide.ps" in the /docs/ps subdirectory of the gnuplot source
distribution contains more examples of the enhanced syntax.
pslatex and pstex
The pslatex and pstex drivers generate output for further processing by
LaTeX and TeX, respectively. Figures generated by pstex can be included
in any plain-based format (including LaTeX).
Syntax:
set terminal pslatex | |pstex {<color>} {<dashed>} {<rotate>}
{auxfile} {<font_size>}
<color> is either color or monochrome. <rotate> is either rotate or
norotate and determines if the y-axis label is rotated. <font_size> is
the size (in pts) of the desired font.
If auxfile is specified, it directs the driver to put the PostScript
commands into an auxiliary file instead of directly into the LaTeX file.
This is useful if your pictures are large enough that dvips cannot handle
them. The name of the auxiliary PostScript file is derived from the name of
the TeX file given on the set output command; it is determined by replacing
the trailing .tex (actually just the final extent in the file name) with
.ps in the output file name, or, if the TeX file has no extension, .ps
is appended. Remember to close the file before leaving gnuplot.
All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '{', you also need to include a '}' at the
end of the text, and the whole text will be centered both horizontally
and vertically by LaTeX. --- If the text string begins with '[', you need
to continue it with: a position specification (up to two out of t,b,l,r),
']{', the text itself, and finally, '}'. The text itself may be anything
LaTeX can typeset as an LR-box. \rule{}{}'s may help for best positioning.
Examples:
set term pslatex monochrome dashed rotate # set to defaults
To write the PostScript commands into the file "foo.ps":
set term pslatex auxfile
set output "foo.tex"; plot ...: set output
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
set title '\LaTeX\ -- $ \gamma $'
Force centering both horizontally and vertically:
set label '{\LaTeX\ -- $ \gamma $}' at 0,0
Specify own positioning (top here):
set xlabel '[t]{\LaTeX\ -- $ \gamma $}'
The other label -- account for long ticlabels:
set ylabel '[r]{\LaTeX\ -- $ \gamma $\rule{7mm}{0pt}'
Linewidths and pointsizes may be changed with set linestyle.
tgif
Tgif is an X11-based drawing tool---it has nothing to do with GIF.
The tgif driver supports different pointsizes (with set pointsize),
different label fonts and font sizes (e.g. set label "Hallo" at x,y font
"Helvetica,34") and multiple graphs on the page. The proportions of the
axes are not changed.
Syntax:
set terminal tgif {portrait | landscape} {<[x,y]>}
{solid | dashed}
{"<fontname>"} {<fontsize>}
where <[x,y]> specifies the number of graphs in the x and y directions on the
page, "<fontname>" is the name of a valid PostScript font, and <fontsize>
specifies the size of the PostScript font. Defaults are portrait, [1,1],
dashed, "Helvetica", and 18.
The solid option is usually prefered if lines are colored, as they often
are in the editor. Hardcopy will be black-and-white, so dashed should be
chosen for that.
Multiplot is implemented in two different ways.
The first multiplot implementation is the standard gnuplot multiplot feature:
set terminal tgif
set output "file.obj"
set multiplot
set origin x01,y01
set size xs,ys
plot ...
...
set origin x02,y02
plot ...
set nomultiplot
See set multiplot for further information.
The second version is the [x,y] option for the driver itself. The advantage
of this implementation is that everything is scaled and placed automatically
without the need for setting origins and sizes; the graphs keep their natural
x/y proportions of 3/2 (or whatever is fixed by set size).
If both multiplot methods are selected, the standard method is chosen and a
warning message is given.
Examples of single plots (or standard multiplot):
set terminal tgif # defaults
set terminal tgif "Times-Roman" 24
set terminal tgif landscape
set terminal tgif landscape solid
Examples using the built-in multiplot mechanism:
set terminal tgif portrait [2,4] # portrait; 2 plots in the x-
# and 4 in the y-direction
set terminal tgif [1,2] # portrait; 1 plot in the x-
# and 2 in the y-direction
set terminal tgif landscape [3,3] # landscape; 3 plots in both
# directions
tkcanvas
This terminal driver generates Tk canvas widget commands based on Tcl/Tk
(default) or Perl. To use it, rebuild gnuplot (after uncommenting or
inserting the appropriate line in "term.h"), then
gnuplot> set term tkcanvas {perltk} {interactive}
gnuplot> set output 'plot.file'
After invoking "wish", execute the following sequence of Tcl/Tk commands:
% source plot.file
% canvas .c
% pack .c
% gnuplot .c
Or, for Perl/Tk use a program like this:
use Tk;
my $top = MainWindow->new;
my $c = $top->Canvas->pack;
my $gnuplot = do "plot.pl";
$gnuplot->($c);
MainLoop;
The code generated by gnuplot creates a procedure called "gnuplot"
that takes the name of a canvas as its argument. When the procedure is
called, it clears the canvas, finds the size of the canvas and draws the plot
in it, scaled to fit.
For 2-dimensional plotting (plot) two additional procedures are defined:
"gnuplot_plotarea" will return a list containing the borders of the plotting
area "xleft, xright, ytop, ybot" in canvas screen coordinates, while the ranges
of the two axes "x1min, x1max, y1min, y1max, x2min, x2max, y2min, y2max" in plot
coordinates can be obtained calling "gnuplot_axisranges".
If the "interactive" option is specified, mouse clicking on a line segment
will print the coordinates of its midpoint to stdout. Advanced actions
can happen instead if the user supplies a procedure named
"user_gnuplot_coordinates", which takes the following arguments:
"win id x1s y1s x2s y2s x1e y1e x2e y2e x1m y1m x2m y2m",
the name of the canvas and the id of the line segment followed by the
coordinates of its start and end point in the two possible axis ranges; the
coordinates of the midpoint are only filled for logarithmic axes.
The current version of tkcanvas supports neither multiplot nor replot.
tpic
The tpic terminal driver supports the LaTeX picture environment with tpic
\specials. It is an alternative to the latex and eepic terminal drivers.
Options are the point size, line width, and dot-dash interval.
Syntax:
set terminal tpic <pointsize> <linewidth> <interval>
where pointsize and linewidth are integers in milli-inches and interval
is a float in inches. If a non-positive value is specified, the default is
chosen: pointsize = 40, linewidth = 6, interval = 0.1.
All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '{', you also need to include a '}' at the
end of the text, and the whole text will be centered both horizontally
and vertically by LaTeX. --- If the text string begins with '[', you need
to continue it with: a position specification (up to two out of t,b,l,r),
']{', the text itself, and finally, '}'. The text itself may be anything
LaTeX can typeset as an LR-box. \rule{}{}'s may help for best positioning.
Examples:
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
set title '\LaTeX\ -- $ \gamma $'
Force centering both horizontally and vertically:
set label '{\LaTeX\ -- $ \gamma $}' at 0,0
Specify own positioning (top here):
set xlabel '[t]{\LaTeX\ -- $ \gamma $}'
The other label -- account for long ticlabels:
set ylabel '[r]{\LaTeX\ -- $ \gamma $\rule{7mm}{0pt}'
graph-menu
The gnuplot graph window has the following options on a pop-up menu
accessed by pressing the right mouse button or selecting Options from the
system menu:
Bring to Top when checked brings the graph window to the top after every
plot.
Color when checked enables color linestyles. When unchecked it forces
monochrome linestyles.
Copy to Clipboard copies a bitmap and a Metafile picture.
Background... sets the window background color.
Choose Font... selects the font used in the graphics window.
Line Styles... allows customization of the line colors and styles.
Print... prints the graphics windows using a Windows printer driver and
allows selection of the printer and scaling of the output. The output
produced by Print is not as good as that from gnuplot's own printer
drivers.
Update wgnuplot.ini saves the current window locations, window sizes, text
window font, text window font size, graph window font, graph window font
size, background color and linestyles to the initialization file
WGNUPLOT.INI.
text-menu
The gnuplot text window has the following options on a pop-up menu accessed
by pressing the right mouse button or selecting Options from the system
menu:
Copy to Clipboard copies marked text to the clipboard.
Paste copies text from the clipboard as if typed by the user.
Choose Font... selects the font used in the text window.
System Colors when selected makes the text window honor the System Colors
set using the Control Panel. When unselected, text is black or blue on a
white background.
Update wgnuplot.ini saves the current text window location, text window
size, text window font and text window font size to the initialisation file
WGNUPLOT.INI.
MENU BAR
If the menu file WGNUPLOT.MNU is found in the same directory as
WGNUPLOT.EXE, then the menu specified in WGNUPLOT.MNU will be loaded.
Menu commands:
[Menu] starts a new menu with the name on the following line.
[EndMenu] ends the current menu.
[--] inserts a horizontal menu separator.
[|] inserts a vertical menu separator.
[Button] puts the next macro on a push button instead of a menu.
Macros take two lines with the macro name (menu entry) on the first line and
the macro on the second line. Leading spaces are ignored. Macro commands:
[INPUT] --- Input string with prompt terminated by [EOS] or {ENTER}
[EOS] --- End Of String terminator. Generates no output.
[OPEN] --- Get name of file to open from list box, with title of list box
terminated by [EOS], followed by default filename terminated by [EOS] or
{ENTER}. This uses COMMDLG.DLL from Windows 3.1.
[SAVE] --- Get name of file to save. Similar to [OPEN]
Macro character substitutions:
{ENTER} --- Carriage Return '\r'
{TAB} --- Tab '\011'
{ESC} --- Escape '\033'
{^A} --- '\001'
...
{^_} --- '\031'
Macros are limited to 256 characters after expansion.
x11
gnuplot provides the x11 terminal type for use with X servers. This
terminal type is set automatically at startup if the DISPLAY environment
variable is set, if the TERM environment variable is set to xterm, or
if the -display command line option is used.
Syntax:
set terminal x11 {reset} {<n>}
Multiple plot windows are supported: set terminal x11 <n> directs the
output to plot window number n. If n>0, the terminal number will be
appended to the window title and the icon will be labeled gplt <n>.
The active window may distinguished by a change in cursor (from default
to crosshair.)
Plot windows remain open even when the gnuplot driver is changed to a
different device. A plot window can be closed by pressing the letter q
while that window has input focus, or by choosing close from a window
manager menu. All plot windows can be closed by specifying reset, which
actually terminates the subprocess which maintains the windows (unless
-persist was specified).
Plot windows will automatically be closed at the end of the session
unless the -persist option was given.
The size or aspect ratio of a plot may be changed by resizing the gnuplot
window.
Linewidths and pointsizes may be changed from within gnuplot with
set linestyle.
For terminal type x11, gnuplot accepts (when initialized) the standard
X Toolkit options and resources such as geometry, font, and name from the
command line arguments or a configuration file. See the X(1) man page
(or its equivalent) for a description of such options.
A number of other gnuplot options are available for the x11 terminal.
These may be specified either as command-line options when gnuplot is
invoked or as resources in the configuration file "/.Xdefaults". They are
set upon initialization and cannot be altered during a gnuplot session.
command-line_options
monochome_options
color_resources
grayscale_resources
line_resources
timefmt
This command applies to timeseries where data are composed of dates/times.
It has no meaning unless the command set xdata time is given also.
Syntax:
set timefmt "<format string>"
show timefmt
The string argument tells gnuplot how to read timedata from the datafile.
The valid formats are:
Format Explanation
%d day of the month, 1--31
%m month of the year, 1--12
%y year, 0--99
%Y year, 4-digit
%j day of the year, 1--365
%H hour, 0--24
%M minute, 0--60
%S second, 0--60
%b three-character abbreviation of the name of the month
%B name of the month
Any character is allowed in the string, but must match exactly. \t (tab) is
recognized. Backslash-octals (\nnn) are converted to char. If there is no
separating character between the time/date elements, then %d, %m, %y, %H, %M
and %S read two digits each, %Y reads four digits and %j reads three digits.
%b requires three characters, and %B requires as many as it needs.
Spaces are treated slightly differently. A space in the string stands for
zero or more whitespace characters in the file. That is, "%H %M" can be used
to read "1220" and "12 20" as well as "12 20".
Each set of non-blank characters in the timedata counts as one column in the
using n:n specification. Thus 11:11 25/12/76 21.0 consists of three
columns. To avoid confusion, gnuplot requires that you provide a complete
using specification if your file contains timedata.
Since gnuplot cannot read non-numerical text, if the date format includes
the day or month in words, the format string must exclude this text. But
it can still be printed with the "%a", "%A", "%b", or "%B" specifier: see
set format for more details about these and other options for printing
timedata. (gnuplot will determine the proper month and weekday from the
numerical values.)
See also set xdata and Time/date for more information.
Example:
set timefmt "%d/%m/%Y\t%H:%M"
tells gnuplot to read date and time separated by tab. (But look closely at
your data---what began as a tab may have been converted to spaces somewhere
along the line; the format string must match what is actually in the file.)
Time Data Demo
view
The set view command sets the viewing angle for splots. It controls how
the 3-d coordinates of the plot are mapped into the 2-d screen space. It
provides controls for both rotation and scaling of the plotted data, but
supports orthographic projections only.
Syntax:
set view <rot_x> {,{<rot_z>}{,{<scale>}{,<scale_z>}}}
show view
where <rot_x> and <rot_z> control the rotation angles (in degrees) in a
virtual 3-d coordinate system aligned with the screen such that initially
(that is, before the rotations are performed) the screen horizontal axis is
x, screen vertical axis is y, and the axis perpendicular to the screen is z.
The first rotation applied is <rot_x> around the x axis. The second rotation
applied is <rot_z> around the new z axis.
<rot_x> is bounded to the [0:180] range with a default of 60 degrees, while
<rot_z> is bounded to the [0:360] range with a default of 30 degrees.
<scale> controls the scaling of the entire splot, while <scale_z> scales
the z axis only. Both scales default to 1.0.
Examples:
set view 60, 30, 1, 1
set view ,,0.5
The first sets all the four default values. The second changes only scale,
to 0.5.
See also set ticslevel.
xlabel
The set xlabel command sets the x axis label. Similar commands set labels
on the other axes.
Syntax:
set xlabel {"<label>"} {<xoff>}{,<yoff>} {"<font>{,<size>}"}
show xlabel
The same syntax applies to x2label, ylabel, y2label and zlabel.
Specifying the constants <xoff> or <yoff> as optional offsets for a label
will move it <xoff> or <yoff> character widths or heights. For example,
" set xlabel -1" will change only the x offset of the xlabel, moving the
label roughly one character width to the left. The size of a character
depends on both the font and the terminal.
<font> is used to specify the font in which the label is written; the units
of the font <size> depend upon which terminal is used.
To clear a label, put no options on the command line, e.g., "set y2label".
The default positions of the axis labels are as follows:
xlabel: The x-axis label is centered below the bottom axis.
ylabel: The position of the y-axis label depends on the terminal, and can be
one of the following three positions:
1. Horizontal text flushed left at the top left of the plot. Terminals that
cannot rotate text will probably use this method. If set x2tics is also
in use, the ylabel may overwrite the left-most x2tic label. This may be
remedied by adjusting the ylabel position or the left margin.
2. Vertical text centered vertically at the left of the plot. Terminals
that can rotate text will probably use this method.
3. Horizontal text centered vertically at the left of the plot. The EEPIC,
LaTeX and TPIC drivers use this method. The user must insert line breaks
using \\ to prevent the ylabel from overwriting the plot. To produce a
vertical row of characters, add \\ between every printing character (but this
is ugly).
zlabel: The z-axis label is centered along the z axis and placed in the space
above the grid level.
y2label: The y2-axis label is placed to the right of the y2 axis. The
position is terminal-dependent in the same manner as is the y-axis label.
x2label: The x2-axis label is placed above the top axis but below the plot
title. It is also possible to create an x2-axis label by using new-line
characters to make a multi-line plot title, e.g.,
set title "This is the title\n\nThis is the x2label"
Note that double quotes must be used. The same font will be used for both
lines, of course.
If you are not satisfied with the default position of an axis label, use set
label instead--that command gives you much more control over where text is
placed.
Please see set syntax for further information about backslash processing
and the difference between single- and double-quoted strings.
xrange
The set xrange command sets the horizontal range that will be displayed.
A similar command exists for each of the other axes, as well as for the
polar radius r and the parametric variables t, u, and v.
Syntax:
set xrange { [{{<min>}:{<max>}}] {{no}reverse} {{no}writeback} }
| restore
show xrange
where <min> and <max> terms are constants, expressions or an asterisk to set
autoscaling. If the data are time/date, you must give the range as a quoted
string according to the set timefmt format. Any value omitted will not be
changed.
The same syntax applies to yrange, zrange, x2range, y2range,
rrange, trange, urange and vrange.
The reverse option reverses the direction of the axis, e.g., set xrange
[0:1] reverse will produce an axis with 1 on the left and 0 on the right.
This is identical to the axis produced by set xrange [1:0], of course.
reverse is intended primarily for use with autoscale.
The writeback option essentially saves the range found by autoscale in
the buffers that would be filled by set xrange. This is useful if you wish
to plot several functions together but have the range determined by only
some of them. The writeback operation is performed during the plot
execution, so it must be specified before that command. To restore
the last saved horizontal range use set xrange restore. For example,
set xrange [-10:10]
set yrange [] writeback
plot sin(x)
set yrange restore
replot x/2
results in a yrange of [-1:1] as found only from the range of sin(x); the
[-5:5] range of x/2 is ignored. Executing show yrange after each command
in the above example should help you understand what is going on.
In 2-d, xrange and yrange determine the extent of the axes, trange
determines the range of the parametric variable in parametric mode or the
range of the angle in polar mode. Similarly in parametric 3-d, xrange,
yrange, and zrange govern the axes and urange and vrange govern the
parametric variables.
In polar mode, rrange determines the radial range plotted. <rmin> acts as
an additive constant to the radius, whereas <rmax> acts as a clip to the
radius---no point with radius greater than <rmax> will be plotted. xrange
and yrange are affected---the ranges can be set as if the graph was of
r(t)-rmin, with rmin added to all the labels.
Any range may be partially or totally autoscaled, although it may not make
sense to autoscale a parametric variable unless it is plotted with data.
Ranges may also be specified on the plot command line. A range given on
the plot line will be used for that single plot command; a range given by
a set command will be used for all subsequent plots that do not specify
their own ranges. The same holds true for splot.
Examples:
To set the xrange to the default:
set xrange [-10:10]
To set the yrange to increase downwards:
set yrange [10:-10]
To change zmax to 10 without affecting zmin (which may still be autoscaled):
set zrange [:10]
To autoscale xmin while leaving xmax unchanged:
set xrange [*:]
xtics
Fine control of the major (labelled) tics on the x axis is possible with the
set xtics command. The tics may be turned off with the set noxtics
command, and may be turned on (the default state) with set xtics. Similar
commands control the major tics on the y, z, x2 and y2 axes.
Syntax:
set xtics {axis | border} {{no}mirror} {{no}rotate}
{ autofreq
| <incr>
| <start>, <incr> {,<end>}
| ({"<label>"} <pos> {,{"<label>"} <pos>}...) }
set noxtics
show xtics
The same syntax applies to ytics, ztics, x2tics and y2tics.
axis or border tells gnuplot to put the tics (both the tics themselves
and the accompanying labels) along the axis or the border, respectively. If
the axis is very close to the border, the axis option can result in tic
labels overwriting other text written in the margin.
mirror tells gnuplot to put unlabelled tics at the same positions on the
opposite border. nomirror does what you think it does.
rotate asks gnuplot to rotate the text through 90 degrees, which will be
done if the terminal driver in use supports text rotation. norotate
cancels this.
The defaults are border mirror norotate for tics on the x and y axes, and
border nomirror norotate for tics on the x2 and y2 axes. For the z axis,
the the {axis | border} option is not available and the default is
nomirror. If you do want to mirror the z-axis tics, you might want to
create a bit more room for them with set border.
set xtics with no options restores the default border or axis if xtics are
being displayed; otherwise it has no effect. Any previously specified tic
frequency or position {and labels} are retained.
Positions of the tics are calculated automatically by default or if the
autofreq option is given; otherwise they may be specified in either of
two forms:
The implicit <start>, <incr>, <end> form specifies that a series of tics will
be plotted on the axis between the values <start> and <end> with an increment
of <incr>. If <end> is not given, it is assumed to be infinity. The
increment may be negative. If neither <start> nor <end> is given, <start> is
assumed to be negative infinity, <end> is assumed to be positive infinity,
and the tics will be drawn at integral multiples of <step>. If the axis is
logarithmic, the increment will be used as a multiplicative factor.
Examples:
Make tics at 0, 0.5, 1, 1.5, ..., 9.5, 10.
set xtics 0,.5,10
Make tics at ..., -10, -5, 0, 5, 10, ...
set xtics 5
Make tics at 1, 100, 1e4, 1e6, 1e8.
set logscale x; set xtics 1,100,10e8
The explicit ("<label>" <pos>, ...) form allows arbitrary tic positions or
non-numeric tic labels. A set of tics is a set of positions, each with its
own optional label. Note that the label is a string enclosed by quotes. It
may be a constant string, such as "hello", may contain formatting information
for converting the position into its label, such as "%3f clients", or may be
empty, "". See set format for more information. If no string is given,
the default label (numerical) is used. In this form, the tics do not need to
be listed in numerical order.
Examples:
set xtics ("low" 0, "medium" 50, "high" 100)
set xtics (1,2,4,8,16,32,64,128,256,512,1024)
set ytics ("bottom" 0, "" 10, "top" 20)
In the second example, all tics are labelled. In the third, only the end
tics are labelled.
However they are specified, tics will only be plotted when in range.
Format (or omission) of the tic labels is controlled by set format, unless
the explicit text of a labels is included in the set xtic (<label>) form.
Minor (unlabelled) tics can be added by the set mxtics command.
In case of timeseries data, position values must be given as quoted dates
or times according to the format timefmt. If the <start>, <incr>, <end>
form is used, <start> and <end> must be given according to timefmt, but
<incr> must be in seconds. Times will be written out according to the format
given on set format, however.
Examples:
set xdata time
set timefmt "%d/%m"
set format x "%b %d"
set xrange ["01/12":"06/12"]
set xtics "01/12", 172800, "05/12"
set xdata time
set timefmt "%d/%m"
set format x "%b %d"
set xrange ["01/12":"06/12"]
set xtics ("01/12", "" "03/12", "05/12")
Both of these will produce tics "Dec 1", "Dec 3", and "Dec 5", but in the
second example the tic at "Dec 3" will be unlabelled.
splot
splot is the command for drawing 3-d plots (well, actually projections on
a 2-d surface, but you knew that). It can create a plot from functions or
a data file in a manner very similar to the plot command.
See plot for features common to the plot command; only differences are
discussed in detail here. Note specifically that the binary and matrix
options (discussed under "datafile-modifiers") are not available for plot.
Syntax:
splot {<ranges>}
<function> | "<datafile>" {datafile-modifiers}}
{<title-spec>} {with <style>}
{, {definitions,} <function> ...}
where either a <function> or the name of a data file enclosed in quotes is
supplied. The function can be a mathematical expression, or a triple of
mathematical expressions in parametric mode.
By default splot draws the xy plane completely below the plotted data.
The offset between the lowest ztic and the xy plane can be changed by set
ticslevel. The orientation of a splot projection is controlled by
set view. See set view and set ticslevel for more information.
The syntax for setting ranges on the splot command is the same as for
plot. In non-parametric mode, the order in which ranges must be given is
xrange, yrange, and zrange. In parametric mode, the order is urange,
vrange, xrange, yrange, and zrange.
The title option is the same as in plot. The operation of with is also
the same as in plot, except that the plotting styles available to splot
are limited to lines, points, linespoints, dots, and impulses; the
error-bar capabilities of plot are not available for splot.
The datafile options have more differences.
data-file
grid_data
splot_overview
data-file
As for plot, discrete data contained in a file can be displayed by
specifying the name of the data file, enclosed in quotes, on the splot
command line.
Syntax:
splot '<file_name>' {binary | matrix}
{index <index list>}
{every <every list>}
{using <using list>}
The special filenames "" and "-" are permitted, as in plot.
In brief, binary and matrix indicate that the the data are in a special
form, index selects which data sets in a multi-data-set file are to be
plotted, every specifies which datalines (subsets) within a single data
set are to be plotted, and using determines how the columns within a single
record are to be interpreted.
The options index and every behave the same way as with plot; using
does so also, except that the using list must provide three entries
instead of two.
The plot options thru and smooth are not available for splot, but
cntrparams and dgrid3d provide limited smoothing cabilities.
Data file organization is essentially the same as for plot, except that
each point is an (x,y,z) triple. If only a single value is provided, it
will be used for z, the datablock number will be used for y, and the index
of the data point in the datablock will be used for x. If two values are
provided, gnuplot gives you an error message. Three values are interpreted
as an (x,y,z) triple. Additional values are generally used as errors, which
can be used by fit.
Single blank records separate datablocks in a splot datafile; splot
treats datablocks as the equivalent of function y-isolines. No line will
join points separated by a blank record. If all datablocks contain the same
number of points, gnuplot will draw cross-isolines between datablocks,
connecting corresponding points. This is termed "grid data", and is required
for drawing a surface, for contouring (set contour) and hidden-line removal
(set hidden3d). See also splot grid data
It is no longer necessary to specify parametric mode for three-column
splots.
binary
example datafile
matrix
binary
splot can read binary files written with a specific format (and on a
system with a compatible binary file representation.)
In previous versions, gnuplot dynamically detected binary data files. It
is now necessary to specify the keyword binary directly after the filename.
Single precision floats are stored in a binary file as follows:
<N+1> <y0> <y1> <y2> ... <yN>
<x0> <z0,0> <z0,1> <z0,2> ... <z0,N>
<x1> <z1,0> <z1,1> <z1,2> ... <z1,N>
: : : : ... :
which are converted into triplets:
<x0> <y0> <z0,0>
<x0> <y1> <z0,1>
<x0> <y2> <z0,2>
: : :
<x0> <yN> <z0,N>
<x1> <y0> <z1,0>
<x1> <y1> <z1,1>
: : :
These triplets are then converted into gnuplot iso-curves and then
gnuplot proceeds in the usual manner to do the rest of the plotting.
A collection of matrix and vector manipulation routines (in C) is provided
in binary.c. The routine to write binary data is
int fwrite_matrix(file,m,nrl,nrl,ncl,nch,row_title,column_title)
An example of using these routines is provided in the file bf_test.c, which
generates binary files for the demo file demo/binary.dem.
The index keyword is not supported, since the file format allows only one
surface per file. The every and using filters are supported. using
operates as if the data were read in the above triplet form.
Binary File Splot Demo.
grid_data
The 3D routines are designed for points in a grid format, with one sample,
datapoint, at each mesh intersection; the datapoints may originate from
either evaluating a function, see set isosamples, or reading a datafile,
see splot datafile. The term "isoline" is applied to the mesh lines for
both functions and data. Note that the mesh need not be rectangular in x
and y, as it may be parameterized in u and v, see set isosamples.
However, gnuplot does not require that format. In the case of functions,
'samples' need not be equal to 'isosamples', i.e., not every x-isoline
sample need intersect a y-isoline. In the case of data files, if there
are an equal number of scattered data points in each datablock, then
"isolines" will connect the points in a datablock, and "cross-isolines"
will connect the corresponding points in each datablock to generate a
"surface". In either case, contour and hidden3d modes may give different
plots than if the points were in the intended format. Scattered data can be
converted to a {different} grid format with set dgrid3d.
The contour code tests for z intensity along a line between a point on a
y-isoline and the corresponding point in the next y-isoline. Thus a splot
contour of a surface with samples on the x-isolines that do not coincide with
a y-isoline intersection will ignore such samples. Try:
set xrange [-pi/2:pi/2]; set yrange [-pi/2:pi/2]
set function style lp
set contour
set isosamples 10,10; set samples 10,10;
splot cos(x)*cos(y)
set samples 4,10; replot
set samples 10,4; replot
Old_bugs
There is a bug in the stdio library for old Sun operating systems (SunOS
Sys4-3.2). The "%g" format for 'printf' sometimes incorrectly prints numbers
(e.g., 200000.0 as "2"). Thus, tic mark labels may be incorrect on a Sun4
version of gnuplot. A work-around is to rescale the data or use the set
format command to change the tic mark format to "%7.0f" or some other
appropriate format. This appears to have been fixed in SunOS 4.0.
Another bug: On a Sun3 under SunOS 4.0, and on Sun4's under Sys4-3.2 and
SunOS 4.0, the 'sscanf' routine incorrectly parses "00 12" with the format
"%f %f" and reads 0 and 0 instead of 0 and 12. This affects data input. If
the data file contains x coordinates that are zero but are specified like
'00', '000', etc, then you will read the wrong y values. Check any data
files or upgrade the SunOS. It appears to have been fixed in SunOS 4.1.1.
Suns appear to overflow when calculating exp(-x) for large x, so gnuplot
gets an undefined result. One work-around is to make a user-defined function
like e(x) = x<-500 ? 0 : exp(x). This affects plots of Gaussians (exp(-x*x))
in particular, since x*x grows quite rapidly.
Microsoft C 5.1 has a nasty bug associated with the %g format for 'printf'.
When any of the formats "%.2g", "%.1g", "%.0g", "%.g" are used, 'printf' will
incorrectly print numbers in the range 1e-4 to 1e-1. Numbers that should be
printed in the %e format are incorrectly printed in the %f format, with the
wrong number of zeros after the decimal point. To work around this problem,
use the %e or %f formats explicitly.
gnuplot, when compiled with Microsoft C, did not work correctly on two VGA
displays that were tested. The CGA, EGA and VGA drivers should probably be
rewritten to use the Microsoft C graphics library. gnuplot compiled with
Borland C++ uses the Turbo C graphics drivers and does work correctly with
VGA displays.
VAX/VMS 4.7 C compiler release 2.4 also has a poorly implemented %g format
for 'printf'. The numbers are printed numerically correct, but may not be in
the requested format. The K&R second edition says that for the %g format, %e
is used if the exponent is less than -4 or greater than or equal to the
precision. The VAX uses %e format if the exponent is less than -1. The VAX
appears to take no notice of the precision when deciding whether to use %e or
%f for numbers less than 1. To work around this problem, use the %e or %f
formats explicitly. From the VAX C 2.4 release notes: e,E,f,F,g,G Result
will always contain a decimal point. For g and G, trailing zeros will not
be removed from the result.
VAX/VMS 5.2 C compiler release 3.0 has a slightly better implemented %g
format than release 2.4, but not much. Trailing decimal points are now
removed, but trailing zeros are still not removed from %g numbers in
exponential format.
The two preceding problems are actually in the libraries rather than in the
compilers. Thus the problems will occur whether gnuplot is built using
either the DEC compiler or some other one (e.g. the latest gcc).
ULTRIX X11R3 has a bug that causes the X11 driver to display "every other"
graph. The bug seems to be fixed in DEC's release of X11R4 so newer releases
of ULTRIX don't seem to have the problem. Solutions for older sites include
upgrading the X11 libraries (from DEC or direct from MIT) or defining
ULTRIX_KLUDGE when compiling the x11.trm file. Note that the kludge is not
an ideal fix, however.
The constant HUGE was incorrectly defined in the NeXT OS 2.0 operating
system. HUGE should be set to 1e38 in plot.h. This error has been corrected
in the 2.1 version of NeXT OS.
Some older models of HP plotters do not have a page eject command 'PG'. The
current HPGL driver uses this command in HPGL_reset. This may need to be
removed for these plotters. The current PCL5 driver uses HPGL/2 for text as
well as graphics. This should be modified to use scalable PCL fonts.
On the Atari version, it is not possible to send output directly to the
printer (using /dev/lp as output file), since CRs are added to LFs in
binary output. As a work-around, write the output to a file and copy it to
the printer afterwards using a shell command.
On AIX 4, the literal 'NaNq' in a datafile causes the special internal value
'not-a-number' to be stored, rather than setting an internal 'undefined'
flag. A workaround is to use set missing 'NaNq'.
There may be an up-to-date list of bugs since the release on the WWW page:
http://www.cs.dartmouth.edu/gnuplot_info.html
Please report any bugs to bug-gnuplot@dartmouth.edu.
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