[Ifeffit] wavelet transforms for EXAFS

[Matt Newville]

Hi Folks,

It's been on my To-Do list for many years, and was one of the arguments for
needing to be able to handle multi-dimensional arrays for EXAFS analysis.
So I'm happy to say that the Continuous Cauchy Wavelet transform of Munuz,
Argoul, and Farges (from American Mineralogist 2003) is now (only ten years
late) available in Larch.   See
http://xraypy.github.io/xraylarch/xafs/wavelets.html  for an example.

The code (see
https://github.com/xraypy/xraylarch/blob/master/plugins/xafs/cauchy_wavelet.py
)
is adopted from the matlab code of M Munoz and F Farges, and that
publication should be used as the citation for this routine.  I know there
are other implementations of wavelet transforms for EXAFS.... suggestions
for changes or additions are welcome, as is additional code.

The ability to actually fit data in wavelet space is not yet implemented.
This was sort of planned for, and so shouldn't be too difficult to do.   If
anyone is interested in trying to fit EXAFS data in wavelet space, please
let me know.

I try to avoid too many announcements about why you should be using Larch
instead of Ifeffit, but this is a clear case of something that was
impossible in Ifeffit, but added as a single file of code (less than 150
lines, including code documentation) to Larch.

--Matt
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