COMBINE-Combine two spectra, adding with weights according to errors

Description:

Combines two spectra, adding them with weights that depend on their errors. Elements with equal errors, for example, will be averaged. COMBINE is intended for use with spectra, but will work on any data that has error values for each data point.

Parameters:

SPECTRUM

The first of the two spectra to be combined.

SPECTRUM1

The second of the two spectra to be combined.

OUTPUT

The name of the resulting spectrum. This can be the same as SPECTRUM, in which case no new spectrum will be created.

Source comments:

 C O M B I N E

 Combine two spectra or images. If error or variance information
 is available on the two images a weighted mean of the two
 is formed. If error information is missing for one or both
 images a simple average is formed.

 Command parameters -

 SPECTRUM  The name of the structure containing the first spectrum

 SPECTRUM1 The name of the structure containing the second spectrum

 OUTPUT    The name of the result of the operation.  This can
           be the same as for SPECTRUM.  If not, a new structure
           is created, with everything but the data a direct
           copy of the input.

                                      JAB / AAO  14th July 1986