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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include <math/gsurfit.h>
+include "dgsurfitdef.h"
+
+# GSFIT -- Procedure to solve the normal equations for a surface.
+# The inner products of the basis functions are calculated and
+# accumulated into the GS_NCOEFF(sf) ** 2 matrix MATRIX.
+# The main diagonal of the matrix is stored in the first row of
+# MATRIX followed by the remaining non-zero diagonals.
+# The inner product
+# of the basis functions and the data ordinates are stored in the
+# GS_NCOEFF(sf)-vector VECTOR. The Cholesky factorization of MATRIX
+# is calculated and stored in CHOFAC. Forward and back substitution
+# is used to solve for the GS_NCOEFF(sf)-vector COEFF.
+
+procedure dgsfit (sf, x, y, z, w, npts, wtflag, ier)
+
+pointer	sf		# surface descriptor
+double	x[npts]		# array of x values
+double	y[npts]		# array of y values
+double	z[npts]		# data array
+double	w[npts]		# array of weights
+int	npts		# number of data points
+int	wtflag		# type of weighting
+int	ier		# ier = OK, everything OK
+			# ier = SINGULAR, matrix is singular, 1 or more
+			# coefficients are 0.
+			# ier = NO_DEG_FREEDOM, too few points to solve matrix
+
+begin
+	    call dgszero (sf)
+	    call dgsacpts (sf, x, y, z, w, npts, wtflag)
+	    call dgssolve (sf, ier)
+end