html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/issues/2035#issuecomment-378125383,https://api.github.com/repos/pydata/xarray/issues/2035,378125383,MDEyOklzc3VlQ29tbWVudDM3ODEyNTM4Mw==,1217238,2018-04-03T04:33:40Z,2018-04-03T04:33:40Z,MEMBER,"If you look at the coordinates, the first and last labels get removed in arithmetic (by default we use an inner join).

You might find it more informative to look at the result of doing arithmetic with an outer join, which *does* result in some NaNs:
```
In [5]: with xr.set_options(arithmetic_join='outer'):
   ...:     print(da[...,1:]-da[...,:-1])
   ...:
<xarray.DataArray (x: 5, y: 5, z: 5)>
array([[[nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan]],

       [[nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan]],

       [[nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan]],

       [[nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan]],

       [[nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan],
        [nan,  0.,  0.,  0., nan]]])
Coordinates:
  * z        (z) int64 0 1 2 3 4
  * x        (x) int64 0 1 2 3 4
  * y        (y) int64 0 1 2 3 4
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,310670696
https://github.com/pydata/xarray/issues/2035#issuecomment-378123622,https://api.github.com/repos/pydata/xarray/issues/2035,378123622,MDEyOklzc3VlQ29tbWVudDM3ODEyMzYyMg==,5635139,2018-04-03T04:19:37Z,2018-04-03T04:19:37Z,MEMBER,"Because it's doing `3.0 - 3.0`? Or am I misunderstanding something?

Try taking a single x & y slice and looking at the input & the output","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,310670696
https://github.com/pydata/xarray/issues/2035#issuecomment-378119865,https://api.github.com/repos/pydata/xarray/issues/2035,378119865,MDEyOklzc3VlQ29tbWVudDM3ODExOTg2NQ==,5635139,2018-04-03T03:49:41Z,2018-04-03T03:49:41Z,MEMBER,Right - it's aligning on the intersection of the overlapping coords - in this case the `z` dim goes from len=4 to len=3,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,310670696