NAME
polfit
DESCRIPTION
subroutine polfit.f
source
Bevington, pages 140-142.
purpose
make least-squares fit to data with a polynomial curve
y = a(1) + a(2)*x + a(3)*x**2 + a(3)*x**3 + . . .
usage
call polfit (x, y, sigmay, npts, nterms, mode, a, chisqr)
description of parameters
x - array of data points for independent variable
y - array of data points for dependent variable
sigmay - array of standard deviations for y data points
npts - number of pairs of data points
nterms - number of coefficients (degree of polynomial + 1)
mode - determines method of weighting least-squares fit
+1 (instrumental) weight(i) = 1./sigmay(i)**2
0 (no weighting) weight(i) = 1.
-1 (statistical) weight(i) = 1./y(i)
a - array of coefficients of polynomial
chisqr - reduced chi square for fit
subroutines and function subprograms required
determ (array, norder)
evaluates the determinant of a symetrical
two-dimension matrix of order norder
comments
valid for nterms up to 10