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authorJoe Hunkeler <jhunkeler@gmail.com>2015-08-11 16:51:37 -0400
committerJoe Hunkeler <jhunkeler@gmail.com>2015-08-11 16:51:37 -0400
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+.help nlerrors Feb91 "Nlfit Package"
+.ih
+NAME
+nlerrors -- compute the fit statistics and errors in the parameters
+.ih
+SYNOPSIS
+nlerrors[rd] (nl, z, zfit, w, npts, variance, chisqr, errors)
+
+.nf
+pointer nl # curve descriptor
+real/double z[npts] # array of input function values
+real/double zfit[npts] # array of fitted function values
+real/double w[npts] # array of weights
+int npts # number of data points
+real/double variance # the computed variance of the fit
+real/double chisqr # the computed reduced chi-square of the fit
+real/double errors[*] # errors in the fitted parameters
+.fi
+.ih
+ARGUMENTS
+.ls nl
+Pointer to the curve descriptor structure.
+.le
+.ls z
+Array of function values.
+.le
+.ls zfit
+Array of fitted function values.
+.le
+.ls w
+Array of weights.
+.le
+.ls npts
+The number of data points.
+.le
+.ls variance
+The computed variance of the fit.
+.le
+.ls chisqr
+The computed reduced chi-squared of the fit.
+.le
+.ls errors
+Array of errors in the computed parameters.
+.le
+.ih
+DESCRIPTION
+Compute the variance and reduced chi-squared of the fit and the
+errors in the fitted parameters.
+.ih
+NOTES
+The reduced chi-squared of the fit is the square root of the sum of the
+weighted squares of the residuals divided by the number of degrees of freedom.
+The variance of the fit is the square root of the sum of the
+squares of the residuals divided by the number of degrees of freedom.
+If the weighting is uniform, then the reduced chi-squared is equal to the
+variance of the fit.
+The error of the j-th parameter is the square root of the j-th diagonal
+element of the inverse of the data matrix. If the weighting is uniform,
+then the errors are scaled by the square root of the variance of the data.
+
+The zfit array can be computed by a call to the nlvector[rd] routine.
+The size of the array required to hold the output error array can be
+determined by a call to nlstati.
+.ih
+SEE ALSO
+nlvector,nlstat
+.endhelp