issues: 1879109770

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
1879109770 PR_kwDOAMm_X85ZbILy 8140 Deprecate passing pd.MultiIndex implicitly 4160723 open 0     23 2023-09-03T14:01:18Z 2023-11-15T20:15:00Z   MEMBER   0 pydata/xarray/pulls/8140
  • Follow-up #8094
  • [x] Closes #6481
  • [x] User visible changes (including notable bug fixes) are documented in whats-new.rst

This PR should normally raise a warning each time when indexed coordinates are created implicitly from a pd.MultiIndex object.

I updated the tests to create coordinates explicitly using Coordinates.from_pandas_multiindex().

I also refactored some parts where a pd.MultiIndex could still be passed and promoted internally, with the exception of:

  • swap_dims(): it should raise a warning! Right now the warning message is a bit confusing for this case, but instead of adding a special case we should probably deprecate the whole method? As it is suggested as a TODO comment... This method was to circumvent the limitations of dimension coordinates, which isn't needed anymore (rename_dims and/or set_xindex is equivalent and less confusing).
  • xr.DataArray(pandas_obj_with_multiindex, dims=...): I guess it should raise a warning too?
  • da.stack(z=...).groupby("z"): it shoudn't raise a warning, but this requires a (heavy?) refactoring of groupby. During building the "grouper" objects, grouper.group1d or grouper.unique_coord may still be built by extracting only the multi-index dimension coordinate. I'd greatly appreciate if anyone familiar with the groupby implementation could help me with this! @dcherian ?
 
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