GNUPlot Manual
GNUPlot Manual
GNUPlot Manual
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36 SET-SHOW gnuplot 4.0 59<br />
set cntrparam { { linear<br />
| cubicspline<br />
| bspline<br />
| points <br />
| order <br />
| levels { auto {} | <br />
| discrete {,{,...}}<br />
| incremental , {,}<br />
}<br />
}<br />
}<br />
show contour<br />
This command has two functions. First, it sets the values of z for which contour points are to be<br />
determined (by linear interpolation between data points or function isosamples.) Second, it controls the<br />
way contours are drawn between the points determined to be of equal z. should be an integral<br />
constant expression and , ... any constant expressions. The parameters are:<br />
linear, cubicspline, bspline — Controls type of approximation or interpolation. If linear, then<br />
straight line segments connect points of equal z magnitude. If cubicspline, then piecewise-linear contours<br />
are interpolated between the same equal z points to form somewhat smoother contours, but which<br />
may undulate. If bspline, a guaranteed-smoother curve is drawn, which only approximates the position<br />
of the points of equal-z.<br />
points — Eventually all drawings are done with piecewise-linear strokes. This number controls the<br />
number of line segments used to approximate the bspline or cubicspline curve. Number of cubicspline<br />
or bspline segments (strokes) = points * number of linear segments.<br />
order — Order of the bspline approximation to be used. The bigger this order is, the smoother the<br />
resulting contour. (Of course, higher order bspline curves will move further away from the original<br />
piecewise linear data.) This option is relevant for bspline mode only. Allowed values are integers in the<br />
range from 2 (linear) to 10.<br />
levels — Selection of contour levels, controlled by auto (default), discrete, incremental, and ,<br />
number of contour levels, limited to<br />
MAX_DISCRETE_LEVELS as defined in plot.h (30 is standard.)<br />
For auto, specifies a nominal number of levels; the actual number will be adjusted to give simple<br />
labels. If the surface is bounded by zmin and zmax, contours will be generated at integer multiples of<br />
dz between zmin and zmax, where dz is 1, 2, or 5 times some power of ten (like the step between two<br />
tic marks).<br />
For levels discrete, contours will be generated at z = , ... as specified; the number of<br />
discrete levels sets the number of contour levels. In discrete mode, any set cntrparam levels <br />
are ignored.<br />
For incremental, contours are generated at values of z beginning at and increasing by<br />
, until the number of contours is reached. is used to determine the number of<br />
contour levels, which will be changed by any subsequent set cntrparam levels .<br />
If the command set cntrparam is given without any arguments specified, the defaults are used: linear,<br />
5 points, order 4, 5 auto levels.<br />
Examples:<br />
set cntrparam bspline<br />
set cntrparam points 7<br />
set cntrparam order 10<br />
To select levels automatically, 5 if the level increment criteria are met:<br />
set cntrparam levels auto 5<br />
To specify discrete levels at .1, .37, and .9:<br />
set cntrparam levels discrete .1,1/exp(1),.9