Pan Deng: Integrating pandas.Panel and xarray Features

[OXPHOS]

• I contacted NumFOCUS mentors before writing my proposal
• I showed you my contribution (it can be any form: proof-of-concept project idea, some sample code or just a link to your commits from other project)
• I linked to my sample contribution from the proposal
• I linked to my opened issues in numfocus/gsoc repository from the proposal

[OXPHOS]

Hey I finished my proposal draft about Panel/xarray integration project. Would you mind have a look at it when you have time? Thanks so much! @shoyer @jreback

[jreback]

currently xarray is pure python, this would be a very large change. using cython and/or numba might be acceptable. I suspect that xarray will eventually have to go down this route. @shoyer can shed some more light.

[shoyer]

xarray is currently pure Python built on top of NumPy and dask.array. Indeed, Cython or Numba might be acceptable, but Numba at least would need to be an optional dependency.

For PCA in particular, it would make sense to wrap existing implementations/wrappers in SciPy rather than rolling your own.

[OXPHOS]

I get it..No experience with cython or SciPy. I will check it out.

[shoyer]

One feature that would have a lot of impact would be bringing groupby performance in xarray up to par with pandas: pydata/xarray#659

[OXPHOS]

Honestly I didn't find too much to transfer from pandas to xarray and I am trying to dig something out from nowhere. Or actually I should focus on add-on features like cummsum, prod and rank, but not basic ones like multiIndex too much?

Also I have the following todo list from pydata/xarray#702. Can I include all this in my proposal?
-[ ] Make levels accessible as coordinate variables (e.g., ds['time'] can pull out the 'time' level of a multi-index)
-[ ] Make isel_points/sel_points return objects with a MultiIndex? (probably after the previous TODO, so we can preserve basic backwards compatibility)
-[ ] Add set_index/reset_index/swaplevel to make it easier to create and manipulate multi-indexes