issues: 564780280

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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
564780280 MDExOlB1bGxSZXF1ZXN0Mzc0OTQ3OTE3 3769 concat now handles non-dim coordinates only present in one dataset 2448579 closed 0     1 2020-02-13T15:55:30Z 2020-02-23T20:48:19Z 2020-02-23T19:45:18Z MEMBER   0 pydata/xarray/pulls/3769
  • [x] Tests added
  • [x] Passes isort -rc . && black . && mypy . && flake8
  • [x] Fully documented, including whats-new.rst for all changes and api.rst for new API

da1 = xr.DataArray([1, 2, 3], dims="x", coords={"x": [1, 2, 3], "y": 1}) da2 = xr.DataArray([4, 5, 6], dims="x", coords={"x": [4, 5, 6]}) xr.concat([da1, da2], dim="x") This use case is quite common since you can get da1 from something like bigger_da1.sel(y=1)

On master this raises an uninformative KeyError because 'y' is not present in all datasets. This is because coords="different" by default which means that we are checking for equality. However coords='different'(and the equality check) is meaningless when the variable is only present in one of the objects to be concatenated.

This PR skips equality checking when a variable is only present in one dataset and raises a nicer error message when it is present in more than one but not all datasets.

 
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