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
354923742,MDU6SXNzdWUzNTQ5MjM3NDI=,2388,Test equality of DataArrays up to transposition,35968931,closed,0,,,2,2018-08-28T22:13:01Z,2018-10-08T12:25:46Z,2018-10-08T12:25:46Z,MEMBER,,,,"While writing some unit tests to check I had wrapped `np.gradient` correctly with `xr.apply_ufunc`, I came unstuck because my results were equivalent except for transposed dimensions. It took me a while to realise that `xarray.testing.asset_equal` considers two DataArrays equal only if their dimensions are in the same order, because intuitively that shouldn't matter in the context of xarray's data model.


A simple example to demonstrate what I mean:
```python
# Create two functionally-equivalent dataarrays
data = np.random.randn(4, 3)
da1 = xr.DataArray(data, dims=('x', 'y'))
da2 = xr.DataArray(data.T, dims=('y', 'x'))

# This test will fail
xarray.tests.assert_equal(da1, da2)
```
This test fails, with output
```
E       AssertionError: <xarray.DataArray (x: 4, y: 3)>
E       array([[ 0.761038,  0.121675,  0.443863],
E              [ 0.333674,  1.494079, -0.205158],
E              [ 0.313068, -0.854096, -2.55299 ],
E              [ 0.653619,  0.864436, -0.742165]])
E       Coordinates:
E         * x        (x) int64 5 7 9 11
E         * y        (y) int64 1 4 6
E       <xarray.DataArray (y: 3, x: 4)>
E       array([[ 0.761038,  0.333674,  0.313068,  0.653619],
E              [ 0.121675,  1.494079, -0.854096,  0.864436],
E              [ 0.443863, -0.205158, -2.55299 , -0.742165]])
E       Coordinates:
E         * x        (x) int64 5 7 9 11
E         * y        (y) int64 1 4 6
```
even though these two DataArrays are functionally-equivalent for all xarray operations you could perform with them.

It would make certain types of unit tests simpler and clearer to have a function like
```python
xarray.tests.assert_equivalent(da1, da2)
```
which would return true if one DataArray can be formed from the other by transposition.

I would have thought that a test that does this would just transpose one into the shape of the other before comparison?","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/2388/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue