@node Contour, Ctype, Connect, Commands

@iftex
@syntax Contour.
@end iftex
@example
Syntax: CONTOUR 
@end example
@pindex Contour
@findex 2-dimensional graphics, contour

Makes a contour plot of an image read by the IMAGE command
(@pxref{Image}).
The contour levels are set using LEVELS;
plot coordinates are taken to be those set by the
LIMITS command, and contours are drawn in the current LTYPE. It is not
possible to produce labeled contours.

Any pixels whose value is @code{NaN} are ignored, as are any whose value
equals the SM variable @code{$missing_data}; by default this is some
very large number.

See also DITHER for dithering images, IMAGE CURSOR for using cursors to
get values from images, MINMAX for finding the minimum and maximum of
images, and Arithmetic for extracting cross-sections of images.