RRDGRAPH(1) rrdtool RRDGRAPH(1)
NNAAMMEE
rrdtool graph - Create a graph based on data from one or
several RRD
SSYYNNOOPPSSIISS
rrrrddttooooll ggrraapphh _f_i_l_e_n_a_m_e [--ss|----ssttaarrtt _s_e_c_o_n_d_s] [--ee|----eenndd _s_e_c_
_o_n_d_s] [--xx|----xx--ggrriidd _x_-_a_x_i_s _g_r_i_d _a_n_d _l_a_b_e_l]
[--yy|----yy--ggrriidd _y_-_a_x_i_s _g_r_i_d _a_n_d _l_a_b_e_l] [----aalltt--yy--ggrriidd]
[----aalltt--aauuttoossccaallee] [----aalltt--aauuttoossccaallee--mmaaxx] [----uunniittss--eexxppoonneenntt]
_v_a_l_u_e]> [--vv|----vveerrttiiccaall--llaabbeell _t_e_x_t] [--ww|----wwiiddtthh _p_i_x_e_l_s]
[--hh|----hheeiigghhtt _p_i_x_e_l_s] [--ii|----iinntteerrllaacceedd] [--ff|----iimmggiinnffoo _f_o_r_
_m_a_t_s_t_r_i_n_g] [--aa|----iimmggffoorrmmaatt GGIIFF|PPNNGG] [--zz|----llaazzyy] [--oo|----lloogg
aarriitthhmmiicc] [--uu|----uuppppeerr--lliimmiitt _v_a_l_u_e]
[--ll|----lloowweerr--lliimmiitt _v_a_l_u_e] [--gg|----nnoo--lleeggeenndd] [--rr|----rriiggiidd]
[----sstteepp _v_a_l_u_e] [--bb|----bbaassee _v_a_l_u_e] [--cc|----ccoolloorr _C_O_L_
_O_R_T_A_G##_r_r_g_g_b_b] [--tt|----ttiittllee _t_i_t_l_e] [DDEEFF::_v_n_a_m_e==_r_r_d::_d_s_-
_n_a_m_e::_C_F] [CCDDEEFF::_v_n_a_m_e==_r_p_n_-_e_x_p_r_e_s_s_i_o_n] [PPRRIINNTT::_v_n_a_m_e::_C_F::_f_o_r_
_m_a_t] [GGPPRRIINNTT::_v_n_a_m_e::_C_F::_f_o_r_m_a_t] [CCOOMMMMEENNTT::_t_e_x_t]
[HHRRUULLEE::_v_a_l_u_e##_r_r_g_g_b_b[::_l_e_g_e_n_d]] [VVRRUULLEE::_t_i_m_e##_r_r_g_g_b_b[::_l_e_g_e_n_d]]
[LLIINNEE{11|22|33}::_v_n_a_m_e[##_r_r_g_g_b_b[::_l_e_g_e_n_d]]]
[AARREEAA::_v_n_a_m_e[##_r_r_g_g_b_b[::_l_e_g_e_n_d]]] [SSTTAACCKK::_v_n_a_m_e[##_r_r_g_g_b_b[::_l_e_g_
_e_n_d]]]
DDEESSCCRRIIPPTTIIOONN
The ggrraapphh functions main purpose is to create graphical
representations of the data stored in one or several RRRRDDs.
Apart from generating graphs, it can also extract numeri
cal reports.
_f_i_l_e_n_a_m_e
The name of the graph to generate. Since rrrrddttooooll out
puts GIFs and PNGs, it's recommended that the filename
end in either _._g_i_f or _._p_n_g. rrrrddttooooll does not enforce
this, however. If the _f_i_l_e_n_a_m_e is set to '-' the
image file will be written to standard out. All other
output will get suppressed.
PNG output is recommended, since it takes up to 40%
less disk space and 20-30% less time to generate than
a GIF file.
If no graph functions are called, the graph will not
be created.
--ss|----ssttaarrtt _s_e_c_o_n_d_s (default end-1day)
The time when the graph should begin. Time in seconds
since epoch (1970-01-01) is required. Negative numbers
are relative to the current time. By default one day
worth of data will be graphed. See also AT-STYLE TIME
SPECIFICATION section in the _r_r_d_f_e_t_c_h documentation
for a detailed explanation on how to specify time.
--ee|----eenndd _s_e_c_o_n_d_s (default now)
The time when the graph should end. Time in seconds
since epoch. See also AT-STYLE TIME SPECIFICATION
section in the _r_r_d_f_e_t_c_h documentation for a detailed
explanation of ways to specify time.
--xx|----xx--ggrriidd _x_-_a_x_i_s _g_r_i_d _a_n_d _l_a_b_e_l (default autoconfigure)
The x-axis label is quite complex to configure. So if
you don't have very special needs, you can rely on the
autoconfiguration to get this right.
If you want no x-grid at all, use the magic setting
nnoonnee.
The x-axis label and grid can be configured, using the
following format:
_G_T_M::_G_S_T::_M_T_M::_M_S_T::_L_T_M:_L_S_T::_L_P_R::_L_F_M
You have to configure three elements making up the
x-axis labels and grid. The base grid (_G_?_?), the major
grid (_M_?_?) and the labels (_L_?_?). The configuration is
based on the idea that you first specify a well known
amount of time (_?_T_M) and then say how many times it
has to pass between each grid line or label (_?_S_T). For
the label you have to define two additional items: The
precision of the label in seconds (_L_P_R) and the strf
time format used to generate the text of the label
(_L_F_M).
The _?_T_M elements must be one of the following key
words: SSEECCOONNDD, MMIINNUUTTEE, HHOOUURR, DDAAYY, WWEEEEKK, MMOONNTTHH or YYEEAARR.
If you wanted a graph with a base grid every 10 min
utes and a major one every hour, with labels every
hour you would use the following x-axis definition.
"MINUTE:10:HOUR:1:HOUR:1:0:%X"
The precision in this example is 0 because the %X for
mat is exact. If the label was the name of the day, we
would have had a precision of 24 hours, because when
you say something like 'Monday' you mean the whole day
and not Monday morning 00:00. Thus the label should be
positioned at noon. By defining a precision of 24
hours or rather 86400 seconds, you make sure that this
happens.
--yy|----yy--ggrriidd _g_r_i_d _s_t_e_p:_l_a_b_e_l _f_a_c_t_o_r (default autoconfigure)
Makes vertical grid lines appear at _g_r_i_d _s_t_e_p inter
val. Every _l_a_b_e_l _f_a_c_t_o_r gridstep, a major grid line is
printed, along with label showing the value of the
grid line.
If you want no y-grid at all set specify the magic
word nnoonnee.
----aalltt--yy--ggrriidd
Place Y grid dynamically based on graph Y range. Algo
rithm ensures that you always have grid, that there
are enough but not too many grid lines and the grid is
metric. That is grid lines are placed every 1, 2, 5 or
10 units. (contributed by Sasha Mikheev)
----aalltt--aauuttoossccaallee
Compute Y range based on function absolute minimum
and maximum values. Default algorithm uses predefined
set of ranges. This is good in many cases but it
fails miserably when you need to graph something like
260 + 0.001 * sin(x). Default algorithm will use Y
range from 250 to 300 and on the graph you will see
almost straight line. With --alt-autoscale Y range
will be from slightly less the 260 - 0.001 to slightly
more then 260 + 0.001 and periodic behavior will be
seen. (contributed by Sasha Mikheev)
----aalltt--aauuttoossccaallee--mmaaxx
Where --alt-autoscale will modify both the absolute
maximum AND minimum values, this option will only
affect the maximum value. The minimum value, if not
defined on the command line, will be 0. This option
can be useful when graphing router traffic when the
WAN line uses compression, and thus the throughput may
be higher than the WAN line speed.
----uunniittss--eexxppoonneenntt _v_a_l_u_e (default autoconfigure)
This sets the 10**exponent scaling of the y-axis val
ues. Normally values will be scaled to the appropri
ate units (k, M, etc.). However you may wish to dis
play units always in k (Kilo, 10e3) even if the data
is in the M (Mega, 10e6) range for instance. Value
should be an integer which is a multiple of 3 between
-18 and 18 inclusive. It is the exponent on the units
you which to use. For example, use 3 to display the
y-axis values in k (Kilo, 10e3, thousands), use -6 to
display the y-axis values in u (Micro, 10e-6, mil
lionths). Use a value of 0 to prevent any scaling of
the y-axis values.
--vv|----vveerrttiiccaall--llaabbeell _t_e_x_t
vertical label on the left side of the graph. This is
normally used to specify the units used.
--ww|----wwiiddtthh _p_i_x_e_l_s (default 400 pixel)
Width of the drawing area within the graph. This
affects the size of the gif.
--hh|----hheeiigghhtt _p_i_x_e_l_s (default 100 pixel)
Width of the drawing area within the graph. This
affects the size of the gif.
--ii|----iinntteerrllaacceedd (default: false)
If you set this option, then the resulting GIF will be
interlaced. Most web browsers display these incremen
tally as they load. If you do not use this option, the
GIFs default to being progressive scanned. The only
effect of this option is to control the format of the
GIF on disk. It makes no changes to the layout or con
tents of the graph.
--ff|----iimmggiinnffoo _f_o_r_m_a_t_s_t_r_i_n_g
After the image has been created, the graph function
uses printf together with this format string to create
output similar to the PRINT function, only that the
printf is supplied with the parameters _f_i_l_e_n_a_m_e, _x_s_i_z_e
and _y_s_i_z_e. In order to generate an IIMMGG tag suitable
for including the graph into a web page, the command
line would look like this:
--imginfo '
'
--aa|----iimmggffoorrmmaatt GGIIFF|PPNNGG (default: GIF)
Allows you to produce PNG output from rrdtool.
--zz|----llaazzyy (default: false)
Only generate the graph, if the current gif is out of
date or not existent.
--uu|----uuppppeerr--lliimmiitt _v_a_l_u_e (default autoconfigure)
Defines the value normally located at the upper border
of the graph. If the graph contains higher values, the
upper border will move upwards to accomodate these
values as well.
If you want to define an upper-limit which will not
move in any event you have to set the ----rriiggiidd option
as well.
--ll|----lloowweerr--lliimmiitt _v_a_l_u_e (default autoconfigure)
This is not the lower limit of a graph. But rather,
this is the maximum lower bound of a graph. For exam
ple, the value -100 will result in a graph that has a
lower limit of -100 or less. Use this keyword to
expand graphs down.
--rr|----rriiggiidd
rigid boundaries mode. Normally rrdgraph will auto
matically expand the lower and upper limit if the
graph contains a value outside the valid range. With
the r option you can disable this behavior
--bb|----bbaassee _v_a_l_u_e
if you are graphing memory (and NOT network traffic)
this switch should be set to 1024 so that one Kb is
1024 byte. For traffic measurement, 1 kb/s is 1000
b/s.
--oo|----llooggaarriitthhmmiicc
logarithmic y-axis scaling
--cc|----ccoolloorr _C_O_L_O_R_T_A_G##_r_r_g_g_b_b (default colors)
override the colors for the standard elements of the
graph. The _C_O_L_O_R_T_A_G must be one of the following sym
bolic names: BBAACCKK ground, CCAANNVVAASS, SSHHAADDEEAA left/top bor
der, SSHHAADDEEBB right/bottom border, GGRRIIDD, MMGGRRIIDD major
grid, FFOONNTT, FFRRAAMMEE and axis of the graph or AARRRROOWW. This
option can be called multiple times to set several
colors.
--gg|----nnoo--lleeggeenndd
Suppress generation of legend; only render the graph.
--tt|----ttiittllee _t_e_x_t (default no title)
Define a title to be written into the graph
----sstteepp _v_a_l_u_e (default automatic)
By default rrdgraph calculates the width of one pixle
in the time domain and tries to get data at that reso
lution from the RRD. With this switch you can override
this behaviour. If you want rrdgraph to get data at 1
hour resolution from the RRD, then you can set the
step to 3600 seconds. Note, that a step smaller than 1
pixle will be silently ignored.
DDEEFF::_v_n_a_m_e==_r_r_d::_d_s_-_n_a_m_e::_C_F
Define virtual name for a data source. This name can
then be used in the functions explained below. The DEF
call automatically chooses an RRRRAA which contains _C_F
consolidated data in a resolution appropriate for the
size of the graph to be drawn. Ideally this means
that one data point from the RRRRAA should be represented
by one pixel in the graph. If the resolution of the
RRRRAA is higher than the resolution of the graph, the
data in the RRA will be further consolidated according
to the consolidation function (_C_F) chosen.
CCDDEEFF::_v_n_a_m_e==_r_p_n_-_e_x_p_r_e_s_s_i_o_n
Create a new virtual data source by evaluating a math
ematical expression, specified in Reverse Polish Nota
tion (RPN). If you have ever used a traditional HP
calculator you already know RPN. The idea behind RPN
notation is, that you have a stack and push your data
onto this stack. When ever you execute an operation,
it takes as many data values from the stack as needed.
The pushing of data is implicit, so when ever you
specify a number or a variable, it gets pushed auto
matically.
If this is all a big load of incomprehensible words
for you, maybe an example helps (a more complete
explanation is given in [1]): The expression _v_n_a_m_e_+_3_/_2
becomes "vname,3,2,/,+" in RPN. First the three values
get pushed onto the stack (which now contains (the
current value of) vname, a 3 and a 2). Then the /
operator pops two values from the stack (3 and 2),
divides the first argument by the second (3/2) and
pushes the result (1.5) back onto the stack. Then the
+ operator pops two values (vname and 1.5) from the
stack; both values are added up and the result gets
pushes back onto the stack. In the end there is only
one value left on the stack: The result of the expres
sion.
The _r_p_n_-_e_x_p_r_e_s_s_i_o_n in the CCDDEEFF function takes both,
constant values as well as _v_n_a_m_e variables. The fol
lowing operators can be used on these values:
+, -, *, /, %
pops two values from the stack applies the
selected operator and pushes the result back onto
the stack. The % operator stands for the modulo
operation.
SIN, COS, LOG, EXP, FLOOR, CEIL
pops one value from the stack, applies the
selected function and pushes the result back onto
the stack.
LT, LE, GT, GE, EQ
pops two values from the stack, compares them
according to the selected condition and pushes
either 1 back onto the stack if the condition is
true and 0 if the condition was not true.
IF pops three values from the stack. If the last
value is not 0, the second value will be pushed
back onto the stack, otherwise the first value is
pushed back.
If the stack contains the values A, B, C, D, E are
presently on the stack, the IF operator will pop
the values E D and C of the stack. It will look at
C and if it is not 0 it will push D back onto the
stack, otherwise E will be sent back to the stack.
MIN, MAX
selects the lesser or larger of the two top stack
values respectively
LIMIT
replaces the value with _*_U_N_K_N_O_W_N_* if it is outside
the limits specified by the two values above it on
the stack.
CDEF:a=alpha,0,100,LIMIT
DUP, EXC, POP
These manipulate the stack directly. DUP will
duplicate the top of the stack, pushing the result
back onto the stack. EXC will exchange the top
two elements of the stack, and POP will pop off
the top element of the stack. Having insufficient
elements on the stack for these operations is an
error.
UN Pops one value off the stack, if it is _*_U_N_K_N_O_W_N_*,
1 will be pushed back otherwise 0.
UNKN
Push an _*_U_N_K_N_O_W_N_* value onto the stack.
PREV
Push _*_U_N_K_N_O_W_N_* if its at the first value of a data
set or otherwise the value of this CDEF at the
previous time step. This allows you to perform
calculations across the data.
INF, NEGINF
Push a positive or negative infinite (oo) value
onto the stack. When drawing an infinite number it
appears right at the top or bottom edge of the
graph, depending whether you have a positive or
negative infinite number.
NOW Push the current (real world) time onto the stack.
TIME
Push the time the current sample was taken onto
the stack. This is the number of non-skip seconds
since 0:00:00 January 1, 1970.
LTIME
This is like TIME ++ ccuurrrreenntt ttiimmeezzoonnee ooffffsseett iinn
sseeccoonnddss. The current offset takes daylight saving
time into account, given your OS supports this. If
you were looking at a sample, in Zurich, in sum
mer, the offset would be 2*3600 seconds, as Zurich
at that time of year is 2 hours ahead of UTC.
Note that the timezone offset is always calculated
for the time the current sample was taken at. It
has nuthing todo with the time you are doing the
calculation.
Please note that you may only use _v_n_a_m_e variables that
you previously defined by either DDEEFF or CCDDEEFF. Further
more, as of this writing (version 0.99.25), you must
use at least one _v_n_a_m_e per expression, that is
"CDEF:fourtytwo=2,40,+" will yield an error message
but not a _v_n_a_m_e fourtytwo that's always equal to 42.
PPRRIINNTT::_v_n_a_m_e::_C_F::_f_o_r_m_a_t
Calculate the chosen consolidation function _C_F over
the data-source variable _v_n_a_m_e and "printf" the result
to stdout using _f_o_r_m_a_t. In the _f_o_r_m_a_t string there
should be a '%lf' or '%le' marker in the place where
the number should be printed.
If an additional '%s' is found AFTER the marker, the
value will be scaled and an appropriate SI magnitude
unit will be printed in place of the '%s' marker. The
scaling will take the '--base' argument into consider
ation!
If a '%S' is used instead of a '%s', then instead of
calculating the appropriate SI magnitude unit for this
value, the previously calculated SI magnitude unit
will be used. This is useful if you want all the val
ues in a PRINT statement to have the same SI magnitude
unit. If there was no previous SI magnitude calcula
tion made, then '%S' behaves like a '%s', unless the
value is 0, in which case it does not remember a SI
magnitude unit and a SI magnitude unit will only be
calculated when the next '%s' is seen or the next '%S'
for a non-zero value.
If you want to put a '%' into your PRINT string, use
'%%' instead.
GGPPRRIINNTT::_v_n_a_m_e::_C_F::_f_o_r_m_a_t
Same as PPRRIINNTT but the result is printed into the graph
below the legend.
CCaavveeaatt:: When using the PPRRIINNTT and GGRRPPRRIINNTT functions to cal
culate data summaries over time periods bounded by the
current time, it is important to note that the last sample
will almost always yield a value of UNKNOWN as it lies
after the last update time. This can result in slight
data skewing, particularly with the AAVVEERRAAGGEE function. In
order to avoid this, make sure that your end time is at
least one heartbeat prior to the current time.
CCOOMMMMEENNTT::_t_e_x_t
Like GGPPRRIINNTT but the _t_e_x_t is simply printed into the
graph.
HHRRUULLEE::_v_a_l_u_e##_r_r_g_g_b_b[::_l_e_g_e_n_d]
Draw a horizontal rule into the graph and optionally
add a legend
VVRRUULLEE::_t_i_m_e##_r_r_g_g_b_b[::_l_e_g_e_n_d]
Draw a vertical rule into the graph and optionally add
a legend
LLIINNEE{11|22|33}::_v_n_a_m_e[##_r_r_g_g_b_b[::_l_e_g_e_n_d]]
Plot for the requested data, using the color speci
fied. Write a legend into the graph. The 3 possible
keywords LLIINNEE11, LLIINNEE22, and LLIINNEE33 generate increasingly
wide lines. If no color is defined, the drawing is
done 'blind' this is useful in connection with the
SSTTAACCKK function when you want to ADD the values of two
data-sources without showing it in the graph.
AARREEAA:_v_n_a_m_e[##_r_r_g_g_b_b[::_l_e_g_e_n_d]]
Does the same as LLIINNEE??, but the area between 0 and the
graph will be filled with the color specified.
SSTTAACCKK:_v_n_a_m_e[##_r_r_g_g_b_b[::_l_e_g_e_n_d]]
Does the same as LLIINNEE??, but the graph gets stacked on
top of the previous LLIINNEE??, AARREEAA or SSTTAACCKK graph.
Depending on the type of the previous graph, the SSTTAACCKK
will be either a LLIINNEE?? or an AARREEAA. This obviously
implies that the first SSTTAACCKK must be preceded by an
AARREEAA or LLIINNEE?? -- you need something to stack something
onto in the first place ;)
Note, that when you STACK onto *UNKNOWN* data, rrdtool
will not draw any graphics ... *UNKNOWN* is not zero
... if you want it to zero then you might want to use
a CDEF argument with IF and UN functions to turn
*UNKNOWN* into zero ...
NNOOTTEESS oonn lleeggeenndd aarrgguummeennttss
EEssccaappiinngg tthhee ccoolloonn
In a ':' in a _l_e_g_e_n_d argument will mark the end of the
legend. To enter a ':' into a legend, the colon must be
escaped with a backslash '\:'. Beware, that many environ
ments look for backslashes themselves, so it may be neces
sary to write two backslashes so that one is passed onto
rrd_graph.
SSttrriinngg FFoorrmmaattttiinngg
The text printed below the actual graph can be formated by
appending special escaped characters at the end of a text.
When ever such a character occurs, all pending text is
pushed onto the graph according to the character speci
fied.
Valid markers are: \\jj for justified, \\ll for left aligned,
\\rr for right aligned and \\cc for centered. In the next sec
tion there is an example showing how to use centered for
mating.
Normally there are two space characters inserted between
every two items printed into the graph. The space follow
ing a string can be suppressed by putting a \\gg at the end
of the string. The \\gg also squshes any space inside the
string if it is at the very end of the string. This can be
used in connection with %%ss to supress empty unit strings.
GPRINT:a:MAX:%lf%s\g
A special case is COMMENT:\\ss this inserts some additional
vertical space before placing the next row of legends.
NNOOTTEE oonn RReettuurrnn VVaalluueess
Whenever rrd_graph gets called, it prints a line telling
the size of the gif it has just created to STDOUT. This
line looks like this: XSIZExYSIZE.
EEXXAAMMPPLLEE 11
rrdtool graph demo.gif --title="Demo Graph" \
DEF:cel=demo.rrd:exhaust:AVERAGE \
"CDEF:far=cel,1.8,*,32,+"" \
LINE2:cel#00a000:"D. Celsius" \
LINE2:far#ff0000:"D. Fahrenheit\c"
EEXXAAMMPPLLEE 22
This example demonstrates the syntax for using IF and UN
to set _*_U_N_K_N_O_W_N_* values to 0. This technique is useful if
you are aggregating interface data where the start dates
of the data sets doesn't match.
rrdtool graph demo.gif --title="Demo Graph" \
DEF:idat1=interface1.rrd:ds0:AVERAGE \
DEF:idat2=interface2.rrd:ds0:AVERAGE \
DEF:odat1=interface1.rrd:ds1:AVERAGE \
DEF:odat2=interface2.rrd:ds1:AVERAGE \
CDEF:agginput=idat1,UN,0,idat1,IF,idat2,UN,0,idat2,IF,+,8,* \
CDEF:aggoutput=odat1,UN,0,odat1,IF,odat2,UN,0,odat2,IF,+,8,* \
AREA:agginput#00cc00:Input Aggregate \
LINE1:aggoutput#0000FF:Output Aggregate
Assuming that idat1 has a data value of _*_U_N_K_N_O_W_N_*, the
CDEF expression
idat1,UN,0,idat1,IF
leaves us with a stack with contents of 1,0,NaN and the IF
function will pop off the 3 values and replace them with
0. If idat1 had a real value like 7942099, then the stack
would have 0,0,7942099 and the real value would be the
replacement.
EEXXAAMMPPLLEE 33
This example shows two ways to use the INF function. First
it makes the background change color during half of the
hours. Then, it uses AREA and STACK to draw a picture. If
one of the inputs was UNKNOWN, all inputs are overlaid
with another AREA.
rrdtool graph example.png --title="INF demo" \
DEF:val1=some.rrd:ds0:AVERAGE \
DEF:val2=some.rrd:ds1:AVERAGE \
DEF:val3=some.rrd:ds2:AVERAGE \
DEF:val4=other.rrd:ds0:AVERAGE \
CDEF:background=val4,POP,TIME,7200,%,3600,LE,INF,UNKN,IF \
CDEF:wipeout=val1,val2,val3,val4,+,+,+,UN,INF,UNKN,IF \
AREA:background#F0F0F0 \
AREA:val1#0000FF:Value1 \
STACK:val2#00C000:Value2 \
STACK:val3#FFFF00:Value3 \
STACK:val4#FFC000:Value4 \
AREA:wipeout#FF0000:Unknown
The first CDEF uses val4 as a dummy value. It's value is
removed immediately from the stack. Then a decision is
made based on the time that a sample was taken. If it is
an even hour (UTC time !) then the area will be filled. If
it is not, the value is set to UNKN and is not plotted.
The second CDEF looks if any of val1,val2,val3,val4 is
unknown. It does so by checking the outcome of
sum(val1,val2,val3,val4). Again, INF is returned when the
condition is true, UNKN is used to not plot the data.
The different items are plotted in a particular order.
First do the background, then use a normal area to overlay
it with data. Stack the other data until they are all
plotted. Last but not least, overlay everything with eye-
hurting red to signal any unknown data.
Note that this example assumes that your data is in the
positive half of the y-axis otherwhise you would would
have to add NEGINF in order to extend the coverage of the
rea to whole graph.
AAUUTTHHOORR
Tobias Oetiker
RREEFFEERREENNCCEESS
[1] http://www.dotpoint.com/xnumber/rpn_or_adl.htm
1.0.35 2002-02-26 RRDGRAPH(1)