linear to log spectral axis conversion

[skendrew]

Is there the ability to convert a Spectrum1D object's spectral axis from linear to log space (and reverse), with flux conservation? I have seen other issues (e.g. #255) discussing resampling/rebinning with or without flux conservation, but I haven't seen this particular case discussed. There are probably numerous implementations of this case out there (e.g. Michele Cappellari's ppxf package has a function called log_rebin - online docs here), would be great to have this integrated into specutils. Its a common step in a lot of analysis that involved radial velocities.

[eteq]

Does not exist, but I agree it's a good idea, @skendrew!

In my experience there's not a "single agreed-upon" way to do this kind of rebinning, though. Do you agree, @skendrew? My default would be to assume the user usually wants the flux-preserving rebinning that's discussed in #255, but onto a log-spaced axis. If that sounds good to you I think that's a good thing to try to target for the next major release.

[skendrew]

this is definitely similar to the discussion in #255 so I have posted further comment there.