sfcontour is a program for generating contour plots of 2-D data. It shares many of its parameters with other 2-D plotting programs, such as sfgrey and sfgraph. You can access these parameters by running sfdoc stdplot.
Let us discuss some of the parameters specific to sfcontour.
The number of contours, their origin and increment are given by nc=, c0=, dc=. If these parameters are not specified, they are determined from the data values. The contour lines in the following picture from jsg/agath/radon were created with sfcontour c0=10 dc=10 nc=10

Alternatively, the contours can be specified in a list with c= or in a file with cfile=.
By default, sfcontour plots only contours for the positive values of the input. If you want both positive and negative values to be represented, use allpos=n.
A 3-D version of sfcontour is sfcontour3.
The contour lines in the following picture from jsg/flat/comaz were created with sfcontour3 cfile=