[AstroPy] ESA Summer of Code in Space 2013

[Joe Harrington]

Just to interject a few quick thoughts into this discussion...

Knowing little of the situation on the ground WRT spectral line fitting,
it does seem to me that it's been done a million times.  If any of those
implementations is decent, OSS, and compiled, why not just wrap it?
Probably the GUI would want to be in Python, but there's a lot of other
stuff under the hood that would be time-consuming and likely slower to
re-(re-re-re-)write.  At the very least, you might save some time by
studying what existing codes do and what people like about them.

Jon Slavin> - robust fitting routines that return error bars on fitted parameters

Regarding the reporting of fits with errors, as many of us have
painfully learned, minimizers don't give these, they only pretend to.
Since that's often not good enough, it would be nice to see a relatively
plug-n-play MCMC (e.g., DE-) put forward as a fitting package.  It would
have to evaluate its own distribution, gave errors, and otherwise
behaved a bit like lmfit.  Yes, there are subtleties to Markov Chains,
but this is also true of minimizers.  Getting something out there and
inviting people to improve it could produce something usable in a few
iterations.  My group can contribute some DE-MCMC code that someone
could adapt.

To Jon's list of requirements, I'd add:

- Able to use a GUI for user-cue input OR take such input from a text
  file
- Able to write such a text file from the GUI user-cue input, for
  subsequent runs (and add to it from a second run, etc.)

One thing that isn't clear to me from the discussion is whether the
scope is merely to identify the center and width vs. pixel number to get
a wavelength solution or calculate Doppler shifts, or whether to do the
whole job of reading multiple line lists, broadening the lines, and
fitting all the lines to the data, returning column densities and
temperatures vs. depth.  In other words, will it calibrate the spectrum
or reproduce it with a model?

--jh--