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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <math/curfit.h>
include "curfitdef.h"
# CVSOLVE -- Solve the matrix normal equations of the form ca = b for a,
# where c is a symmetric, positive semi-definite, banded matrix with
# CV_NCOEFF(cv) rows and a and b are CV_NCOEFF(cv)-vectors.
# Initially c is stored in the CV_ORDER(cv) by CV_NCOEFF(cv) matrix MATRIX
# and b is stored in VECTOR.
# The Cholesky factorization of MATRIX is calculated and stored in CHOFAC.
# Finally the coefficients are calculated by forward and back substitution
# and stored in COEFF.
procedure cvsolve (cv, ier)
pointer cv # curve descriptor
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
int nfree
begin
ier = OK
nfree = CV_NPTS(cv) - CV_NCOEFF(cv)
if (nfree < 0) {
ier = NO_DEG_FREEDOM
return
}
# calculate the Cholesky factorization of the data matrix
call rcvchofac (MATRIX(CV_MATRIX(cv)), CV_ORDER(cv), CV_NCOEFF(cv),
CHOFAC(CV_CHOFAC(cv)), ier)
# solve for the coefficients by forward and back substitution
call rcvchoslv (CHOFAC(CV_CHOFAC(cv)), CV_ORDER(cv), CV_NCOEFF(cv),
VECTOR(CV_VECTOR(cv)), COEFF(CV_COEFF(cv)))
end
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