GNUPlot Manual

36 SET-SHOW gnuplot 4.0 61
36.12 Contour
set contour enables contour drawing for surfaces. This option is available for splot only.
Syntax:
set contour {base | surface | both}
unset contour
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 (p. 58) for the parameters that affect the drawing of contours, and set clabel
(p. 58) for control of labelling of the contours.
The surface can be switched off (see set surface (p. 99)), 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:
unset surface
set contour
set cntrparam ...
set term table
set out ’filename’
splot ...
set out
# contour info now in filename
set term
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 (p. 155).
If contours are desired from non-grid data, set dgrid3d can be used to create an appropriate grid. See
set dgrid3d (p. 63) for more information. See also
and
contours demo (contours.dem)
contours with user defined levels demo (discrete.dem).
36.13 Data style
This form of the command is deprecated. Please see set style data (p. 93).
36.14 Datafile
The set datafile command options control interpretation of fields read from input data files by the
plot, splot, and fit commands. Three such options are currently implemented.
36.14.1 Set datafile missing
The set datafile missing command allows you to tell gnuplot what character string is used in a data
file to denote missing data. Exactly how this missing value will be treated depends on the using specifier
of the plot or splot command.
Syntax: