XCOPI-Like XCOPY but interpolates X-data from 2 files

Description:

The main use of this task is to set the axis data in a data file to values intermediate between those of two other files. Typically, the first file will be a spectrum, the others will be arcs taken either side of the spectrum. The whole axis structure from the first 'arc' file replaces that from the original file, and then the axis data array is modified to give the required intermediate result.

Parameters:

SPECTRUM

File requiring X data.

ARC

File containing X data.

ARC2

Second file containing X data.

FRACTION

Fraction in the relationship:

X data OUTPUT=ARC+(ARC2-ARC1)*FRACTION.

OUTPUT

Name of resulting file.

Source comments:

 X C O P I

 The main use of this routine is to set the axis data in
 a data file to values intermediate between those of
 two other files.  Typically, the first file will be a
 spectrum, the others will be arcs taken either side
 of the spectrum.  The whole axis structure from the first
 'arc' file replaces that from the original file, and then
 the axis data array is modified to give the required
 intermediate result.

 Command parameters -

 SPECTRUM    (Character) The file name of the spectrum whose
             data is to be combined with the axis data from the
             arcs.

 ARC         (Character) The file name of the arc spectrum - i.e.
             the spectrum whose axis information is to be used.

 ARC2        (Character) The file name of the second arc
             spectrum whose axis array is to be used.

 FRACTION    (Numeric) The fractional value controlling the
             weight given to the different arc data arrays.
             If 0., the output data is the same as for ARC,
             and the simpler XCOPY routine should be used.
             If 1., the output data is the same as for ARC2.
             If .5, the output is the average of the two arcs.
             Etc.

 OUTPUT      (Character) The file name for the resulting data
             structure.  If this is the same as SPECTRUM, the
             axis data in SPECTRUM will be changed in situ.

 Command keywords - None

 User variables used - None

                                         KS / CIT 1st July 1983