issues: 325439138

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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
325439138 MDU6SXNzdWUzMjU0MzkxMzg= 2171 Support alignment/broadcasting with unlabeled dimensions of size 1 1217238 open 0     5 2018-05-22T19:52:21Z 2022-04-19T03:15:24Z   MEMBER      

Sometimes, it's convenient to include placeholder dimensions of size 1, which allows for removing any ambiguity related to the order of output dimensions.

Currently, this is not supported with xarray: ```

xr.DataArray([1], dims='x') + xr.DataArray([1, 2, 3], dims='x') ValueError: arguments without labels along dimension 'x' cannot be aligned because they have different dimension sizes: {1, 3}

xr.Variable(('x',), [1]) + xr.Variable(('x',), [1, 2, 3]) ValueError: operands cannot be broadcast together with mismatched lengths for dimension 'x': (1, 3) ```

However, these operations aren't really ambiguous. With size 1 dimensions, we could logically do broadcasting like NumPy arrays, e.g., ```

np.array([1]) + np.array([1, 2, 3]) array([2, 3, 4]) ```

This would be particularly convenient if we add keepdims=True to xarray operations (#2170).

 
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