gnuplot documentation

152 gnuplot 4.3 72 SPLOT
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 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.
72.1.3 Matrix ascii
The matrix keyword (without a sequent binary keyword) in
{s}plot ’a.dat’ matrix
indicates that data are stored in an ascii numbers matrix format.
The z-values are read in a row at a time, i. e.,
z11 z12 z13 z14 ...
z21 z22 z23 z24 ...
z31 z32 z33 z34 ...
and so forth.
In 3D, the x- and y-indices of the matrix surface plot correspond to column and row indices of the
matrix, respectively, being enumerated from 0. You can rescale or transform the axes as usual for a data
file with three columns by means of x=$1, y=$2, z=$3. For example
splot ’a.dat’ matrix using (1+$1/100):(1+$2*10):3
A blank line or comment line ends the matrix, and starts a new surface mesh. You can select among
the meshes inside a file by the index option to the splot command, as usual.
See matrix (p. 152) for examples of plotting rows and columns of the matrix in a 2D plot.
72.1.4 Matrix
Datafile can be in an ascii or binary matrix format. The matrix flag indicates that the file is ascii,
the binary or matrix binary stands for a binary format. For details, see matrix ascii (p. 152) and
matrix binary (p. 151).
Basic usage in splot:
splot ’a.dat’ matrix
splot ’a.gpbin’ {matrix} binary
Advanced usage in splot:
splot ’a.dat’ matrix using 1:2:3
splot ’a.gpbin’ {matrix} binary using 1:2:3