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-378123085,https://api.github.com/repos/pydata/xarray/issues/2035,378123085,MDEyOklzc3VlQ29tbWVudDM3ODEyMzA4NQ==,13205162,2018-04-03T04:15:29Z,2018-04-03T04:15:29Z,CONTRIBUTOR,@maxim-lian But my last point remains: should this really return a zero-valued matrix? I feel like this is counter-intuitive,"{""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
https://github.com/pydata/xarray/issues/2035#issuecomment-378114226,https://api.github.com/repos/pydata/xarray/issues/2035,378114226,MDEyOklzc3VlQ29tbWVudDM3ODExNDIyNg==,13205162,2018-04-03T03:08:07Z,2018-04-03T03:08:07Z,CONTRIBUTOR,"I just realized this is probably the expected behavior (although counter-intuitive for me) since the coordinates of the points I'm operating on are different. I still don't understand why the returned array has zero values though, instead of nans.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,310670696