---
name: "polfit"
section: "3m"
platform: "linux"
package: "iraf"
version: "2.11.3-2"
release: "Debian 3.0 (Woody)"
platforms: ["linux"]
url: "https://new.carta.tech/polfit"
---

# polfit(3m)

## 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