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(gnuplot.info)example datafile

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Enter node , (file) or (file)node

 A simple example of plotting a 3-d data file is

       splot 'datafile.dat'

 where the file "datafile.dat" might contain:

       # The valley of the Gnu.
          0 0 10
          0 1 10
          0 2 10

          1 0 10
          1 1 5
          1 2 10

          2 0 10
          2 1 1
          2 2 10

          3 0 10
          3 1 0
          3 2 10

 Note that "datafile.dat" defines a 4 by 3 grid ( 4 rows of 3 points each ).
 Rows (datablocks) are separated by blank records.

 Note also that the x value is held constant within each dataline.  If you
 instead keep y constant, and plot with hidden-line removal enabled, you will
 find that the surface is drawn 'inside-out'.

 Actually for grid data it is not necessary to keep the x values constant
 within a datablock, nor is it necessary to keep the same sequence of y
 values.  `gnuplot` (Note: gnuplot ) requires only that the number of points
 be the same for each datablock.  However since the surface mesh, from which
 contours are derived, connects sequentially corresponding points, the effect
 of an irregular grid on a surface plot is unpredictable and should be
 examined on a case-by-case basis.