gnuplot documentation

72 SPLOT gnuplot 4.3 151
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 (p. 153).
It is no longer necessary to specify parametric mode for three-column splots.
72.1.1 Binary matrix
Gnuplot can read matrix binary files by use of the option binary appearing without keyword qualifications
unique to general binary, i.e., array, record, format, or filetype. Other general binary keywords
for translation should also apply to matrix binary. (See binary general (p. 66) for more details.)
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:
...
...
...
: : : : ... :
which are converted into triplets:
: : :
: : :
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.
See also binary general (p. 66) and
Binary File Splot Demo.
72.1.2 Example datafile
A simple example of plotting a 3D 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