Only objects of classes raw_spct, cps_spct, and object_spct normally contain
multiple columns of spectral data. These are supported as well as
generic_spct. Is the wide spectra contain multiple spectra in long form,
the original idfactor
is preserved.
Spectra that are already in long form, if passed as argument, are returned
unchanged.
Because the classes defined for spectra have a well defined format, and
known column names we can define a rather simple function for this
operation.