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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <math/gsurfit.h>
include "dgsurfitdef.h"
# GSGCOEFF -- Procedure to fetch a particular coefficient.
# If the requested coefficient is undefined then INDEF is returned.
double procedure dgsgcoeff (sf, xorder, yorder)
pointer sf # pointer to the surface fitting descriptor
int xorder # X order of desired coefficent
int yorder # Y order of desired coefficent
int i, n, maxorder, xincr
begin
if ((xorder > GS_XORDER(sf)) || (yorder > GS_YORDER(sf)))
return (INDEFD)
switch (GS_XTERMS(sf)) {
case GS_XNONE:
if (yorder == 1)
n = xorder
else if (xorder == 1)
n = GS_NXCOEFF(sf) + yorder - 1
else
return (INDEFD)
case GS_XHALF:
maxorder = max (GS_XORDER(sf) + 1, GS_YORDER(sf) + 1)
if ((xorder + yorder) > maxorder)
return (INDEFD)
n = xorder
xincr = GS_XORDER(sf)
do i = 2, yorder {
n = n + xincr
if ((i + GS_XORDER(sf) + 1) > maxorder)
xincr = xincr - 1
}
case GS_XFULL:
n = xorder + (yorder - 1) * GS_NXCOEFF(sf)
}
return (COEFF(GS_COEFF(sf) + n - 1))
end
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