gnuplot documentation

92 gnuplot 4.3 70 SET-SHOW
For backward compatibility with older versions, the following forms are also permitted:
set clip
unset clip
set clip is synonymous with set clip points; unset clip turns off all three types of clipping.
70.10 Cntrparam
set cntrparam controls the generation of contours and their smoothness for a contour plot.
contour displays current settings of cntrparam as well as contour.
Syntax:
set cntrparam { { linear
| cubicspline
| bspline
| points
| order
| levels { auto {} |
| discrete {,{,...}}
| incremental , {,}
}
}
}
show contour
show
This command has two functions. First, it sets the values of z for which contour points are to be
determined (by linear interpolation between data points or function isosamples.) Second, it controls the
way contours are drawn between the points determined to be of equal z. should be an integral
constant expression and , ... any constant expressions. The parameters are:
linear, cubicspline, bspline — Controls type of approximation or interpolation. If linear, then
straight line segments connect points of equal z magnitude. If cubicspline, then piecewise-linear contours
are interpolated between the same equal z points to form somewhat smoother contours, but which
may undulate. If bspline, a guaranteed-smoother curve is drawn, which only approximates the position
of the points of equal-z.
points — Eventually all drawings are done with piecewise-linear strokes. This number controls the
number of line segments used to approximate the bspline or cubicspline curve. Number of cubicspline
or bspline segments (strokes) = points * number of linear segments.
order — Order of the bspline approximation to be used. The bigger this order is, the smoother the
resulting contour. (Of course, higher order bspline curves will move further away from the original
piecewise linear data.) This option is relevant for bspline mode only. Allowed values are integers in the
range from 2 (linear) to 10.
levels — Selection of contour levels, controlled by auto (default), discrete, incremental, and ,
number of contour levels.
For auto, specifies a nominal number of levels; the actual number will be adjusted to give simple
labels. If the surface is bounded by zmin and zmax, contours will be generated at integer multiples of
dz between zmin and zmax, where dz is 1, 2, or 5 times some power of ten (like the step between two
tic marks).
For levels discrete, contours will be generated at z = , ... as specified; the number of
discrete levels sets the number of contour levels. In discrete mode, any set cntrparam levels
are ignored.
For incremental, contours are generated at values of z beginning at and increasing by
, until the number of contours is reached. is used to determine the number of
contour levels, which will be changed by any subsequent set cntrparam levels . If the z axis is
logarithmic, will be interpreted as a factor, just like in set ztics.