FITLINE - Fit a straight line to the data

Description:

If the y-axis error data are available and the WEIGHT parameter is TRUE, this application will perform a weighted least squares fit to a straight line for the data over the range delimited by the XMIN and XMAX parameters. If the y-axis error data are not available or WEIGHT is FALSE, an unweighted fit is performed. The best fit straight line is plotted. The resultant fit parameters are displayed along with some simple statistics for the data (these statistics are also weighted in the case of a weighted fit).

Usage:

fitline [colour]

Parameters:

COLOUR = _INTEGER (Read and Write)

The colour index used when plotting the fitted line.

If the value is not specified on the command line, the current value is used. If there is no current value, a default value of 2 (i.e. red) is used.

WEIGHT =_LOGICAL (Read and Write)

Whether the fit is to use the y-axis error data in the EYCOL data area, if available. If no error data are available, the fit will always be unweighted.

If the value is not specified on the command line, the current value is used. If there is no current value, a default value of TRUE is used.

XMIN = _REAL (Read)

The minimum X value to be used in the fit.

The value of the global parameter PONGO_XMIN is used. If PONGO_XMIN is not defined, the default value 0.0 is used.

XMAX = _REAL (Read)

The maximum X value to be used in the fit.

The value of the global parameter PONGO_XMAX is used. If PONGO_XMAX is not defined, the default value 1.0 is used.