GNUPlot Manual
GNUPlot Manual
GNUPlot Manual
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82 gnuplot 4.0 36 SET-SHOW<br />
trange, urange, and vrange. These ranges may be set directly with set trange, set urange, and set<br />
vrange, or by specifying the range on the plot or splot commands. Currently the default range for<br />
these parametric variables is [-5:5]. Setting the ranges to something more meaningful is expected.<br />
36.47 Plot<br />
The show plot command shows the current plotting command as it results from the last plot and/or<br />
splot and possible subsequent replot commands.<br />
In addition, the show plot add2history command adds this current plot command into the history.<br />
It is useful if you have used replot to add more curves to the current plot and you want to edit the<br />
whole command now.<br />
36.48 Pm3d<br />
pm3d is an splot style for drawing palette-mapped 3d and 4d data as color/gray maps and surfaces. It<br />
uses a pm3d algorithm which allows plotting gridded as well as non-gridded data without preprocessing,<br />
even when the data scans do not have the same number of points.<br />
Drawing of color surfaces is available on terminals supporting filled colored polygons with color mapping<br />
specified by palette. Currently supported terminals include<br />
Screen terminals:<br />
OS/2 Presentation Manager<br />
X11<br />
Linux VGA (vgagl)<br />
GGI<br />
Windows<br />
AquaTerm (Mac OS X)<br />
Files:<br />
PostScript<br />
pslatex, pstex, epslatex<br />
gif, png, jpeg<br />
(x)fig<br />
tgif<br />
cgm<br />
pdf<br />
svg<br />
Let us first describe how a map/surface is drawn. The input data come from an evaluated function or<br />
from an splot data file. Each surface consists of a sequence of separate scans (isolines). The pm3d<br />
algorithm fills the region between two neighbouring points in one scan with another two points in the<br />
next scan by a gray (or color) according to z-values (or according to an additional ’color’ column, see<br />
help for using (p. 43)) of these 4 corners; by default the 4 corner values are averaged, but this can<br />
be changed by the option corners2color. In order to get a reasonable surface, the neighbouring scans<br />
should not cross and the number of points in the neighbouring scans should not differ too much; of<br />
course, the best plot is with scans having same number of points. There are no other requirements (e.g.<br />
the data need not be gridded). Another advantage is that the pm3d algorithm does not draw anything<br />
outside of the input (measured or calculated) region.<br />
Surface coloring works with the following input data:<br />
1. splot of function or of data file with one or three data columns: The gray/color scale is obtained<br />
by mapping the averaged (or corners2color) z-coordinate of the four corners of the above-specified<br />
quadrangle into the range [min color z,max color z] of zrange or cbrange providing a gray value in the<br />
range [0:1]. This value can be used directly as the gray for gray maps. The normalized gray value can<br />
be further mapped into a color — see set palette (p. 85) for the complete description.<br />
2. splot of data file with two or four data columns: The gray/color value is obtained by using the<br />
last-column coordinate instead of the z-value, thus allowing the color and the z-coordinate be mutually