Cntrparam

Sets the different parameters for the contouring plot (see also contour).

Syntax:

 set cntrparam { { linear | cubicspline | bspline } |
    points <n> |
    order <n>  |
    levels { [ auto ] <n> |
    discrete <z1>,<z2>, ... |
    incremental {<start>, <incr>{, <end>} } }

Examples:

    set cntrparam bspline
    set cntrparam points 7
    set cntrparam order 10
    set cntrparam levels auto 5                   # 5 automatic levels
    set cntrparam levels discrete .1,1/exp(1),.9  # 3 discrete at .1,.37,.9
    set cntrparam levels incremental  0,.1,.4
    # 5 incremental levels at 0, .1, .2, .3 and .4
    set cntrparam levels 10
    # sets n = 10 retaining current setting of auto, discr. and
    # increment's start and increment value, while changing end
    set cntrparam levels incremental 100,50
    # set start = 100 and increment = 50, retaining n levels

This command controls the way contours are plotted. <n> should be an integral constant expression and <z1>, <z2> any constant expressions. The parameters are:

linear, cubicspline, bspline - Controls type of approximation or interpolation. If linear, then the contours are drawn piecewise linear, as extracted from the surface directly. If cubicspline, then piecewise linear contours are interpolated to form a somewhat smoother contours, but which may undulate. The third option is the uniform bspline, which only approximates the piecewise linear data but is guaranteed to be smoother.

points - Eventually all drawings are done with piecewise linear strokes. This number controls the number of points used to approximate a curve. Relevant for cubicspline and bspline modes only.

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 - Number of contour levels, 'n'. Selection of the levels is controlled by 'auto' (default), 'discrete', and 'incremental'. For 'auto', if the surface is bounded by zmin and zmax then contours will be generated from zmin+dz to zmax-dz in steps of size dz, where dz = (zmax - zmin) / (levels + 1). For 'discrete', contours will be generated at z = z1, z2 ... as specified. The number of discrete levels is limited to MAX_DISCRETE_LEVELS, defined in plot.h to be 30. If 'incremental', contours are generated at <n> values of z beginning at <start> and increasing by <increment>.