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In this document we fully described the current status of the ACCUMULATE and AVERAGE commands of CLASS, applied on spectra. They are very often
used, and for different purposes, e.g. averaging a set of spectra or
concatenating them. User must be warned about several traps that he
- averaging a set of spectra with successive calls to AVERAGE may
lead into different results than averaging the whole set with
a single call to the command,
- averaging non-aligned spectra must invoke at one point a
resampling. User can do it himself or rely on the internal
resampling loops of the commands. The resampling has
non-trivial effect of the weights.
As a solution to the first problem, the question of saving a weight
array (one weight per channel) in the CLASS data format has been
raised. This would have consequences in particular in term of disk