[S] Points in or out of polygon

Gebhart, Kristi (Gebhart@CIRA.colostate.edu)
Wed, 4 Mar 1998 09:52:45 -0700

Hi S-PLUSers,
I have a need to determine whether or not points are in or out of
arbitrarily shaped and located polygons. Has anyone written an S-PLUS
function that would do something like, given the x-y coordinates of the
vertices of a polygon, determine whether the x-y coordinates of another
point are inside or outside of it?

Many years ago I wrote one in FORTRAN, but I'm clueless as to how to
link FORTRAN to S-PLUS and don't have the Watcom compiler. This is a
task that I know gets used in graphics applications (i.e. to determine
which pixels get painted in a fill). Is there any chance that there's a
graphics library function that already does something like this? If not
I guess I'll get busy and translate my old subroutine.

Thanks, KG
Kristi A. Gebhart
Research Physical Scientist
National Park Service, Air Resources Division
CIRA, Colorado State University
Fort Collins, CO 80523
(970) 491-3684 (voice)
(970) 491-8598 (fax)

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