pydata / pydata/xarray

Scalar coords vs. concat

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Description

Why does this work:

>> import xarray
>> a = xarray.DataArray([1, 2, 3], dims=['x'], coords={'y': 10})
>> b = xarray.DataArray([4, 5, 6], dims=['x'])
>> a + b
<xarray.DataArray (x: 3)>
array([5, 7, 9])
Coordinates:
    y        int64 10

But this doesn't?

>> xarray.concat([a, b], dim='x')
KeyError: 'y'

It doesn't seem coherent to me...

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Research direction

Reproduce the two examples from the issue, comparing scalar-coordinate handling in arithmetic with xarray.concat along the x dimension. Read the concat entry point and the surrounding coordinate-alignment behavior; done means the two operations have a documented and consistent outcome, covered by a regression test.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
data
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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