.TH XFIT 3M
.SH NAME
xfit
.SH DESCRIPTION
subroutine xfit.f

source
  Bevington, page 76.

purpose
  calculate mean and estimated errors for set of data points

usage
  call xfit (x, sigmax, npts, mode, xmean, sigmam, sigma)

description of parameters
  x      - array of data points
  sigmax - array of standard deviations for data points
  npts   - number of data points
  mode   - determines method of weighting
           +1 (instrumental) weight(i) = 1./sigmax(i)**2
            0 (no weighting) weight(i) = 1.
           -1 (statistical)  weight(i) = 1.
  xmean  - weighted mean
  sigmam - standard deviation of mean
  sigma  - standard deviation of data

subroutines and function subprograms required
  none