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/3694#issuecomment-575104969,https://api.github.com/repos/pydata/xarray/issues/3694,575104969,MDEyOklzc3VlQ29tbWVudDU3NTEwNDk2OQ==,10194086,2020-01-16T11:15:25Z,2020-01-16T11:15:25Z,MEMBER,"Sorry for the noise, I do live thinking...

---

However, if I do (2) there is a different behavior for `(d1 * d2).sum()` and `d1 @ d2` in one case:

``` python
with xr.set_options(arithmetic_join=""exact""):
    xr.dot(d2, d3) # -> array(8)
    (d2 * d3).sum() # -> ValueError
```

So?
``` python
join = OPTIONS[""arithmetic_join""]
if join not in [""exact"", ""inner""]:
    join = ""inner""
```


","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,549679475
https://github.com/pydata/xarray/issues/3694#issuecomment-575097853,https://api.github.com/repos/pydata/xarray/issues/3694,575097853,MDEyOklzc3VlQ29tbWVudDU3NTA5Nzg1Mw==,10194086,2020-01-16T10:56:40Z,2020-01-16T10:57:08Z,MEMBER,"On second thought, even with implemented `skipna` the result will not differ between `join=""inner""`, `join=""left""` `join=""right""`, and `join=""outer""`; i.e.:

``` python
with xr.set_options(arithmetic_join=""outer""):
    print((d1 * d2).sum()) # -> 38
```
So I guess (2) is fine.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,549679475
https://github.com/pydata/xarray/issues/3694#issuecomment-575094227,https://api.github.com/repos/pydata/xarray/issues/3694,575094227,MDEyOklzc3VlQ29tbWVudDU3NTA5NDIyNw==,10194086,2020-01-16T10:47:33Z,2020-01-16T10:47:33Z,MEMBER,"I started with a PR using `join = OPTIONS[""arithmetic_join""]` but then I realized that `dot` does not support `skipna`. Thus `join=""left""` `join=""right""`, and `join=""outer""` returns `NaN` for nonequal coords, which I think defeats the purpose. I can

1) Use `OPTIONS[""arithmetic_join""]` anyway
2) Only support `join=""inner""` (i.e. hard-code it in the call to `apply_ufunc`)
3) try to implement `skipna` for `dot` (in a separate PR)
4) Other?

(3) is certainly the largest change but *may* be as easy as `da.fillna(0.)`. Thoughts?

``` python
import numpy as np
import xarray as xr

d1 = xr.DataArray([2, 3, 5, np.NaN])
d2 = xr.DataArray([2, 3, 5, 7])

xr.dot(d1, d2) # -> NaN

xr.dot(d1.fillna(0.), d2) # -> 38
(d1 * d2).sum() # -> 38

```

I use this at:
https://github.com/pydata/xarray/blob/3cc00c121931b5dc0247b4ea5809c4051a4dacdd/xarray/core/weighted.py#L142-L149","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,549679475
https://github.com/pydata/xarray/issues/3694#issuecomment-574544180,https://api.github.com/repos/pydata/xarray/issues/3694,574544180,MDEyOklzc3VlQ29tbWVudDU3NDU0NDE4MA==,1217238,2020-01-15T08:09:21Z,2020-01-15T08:09:21Z,MEMBER,"You could dig through the original PRs to be sure, but I think we mostly picked `join='exact'` out of an abundance of caution. In principle I think it would be reasonable to change it, there is a pretty good case that `(d1 * d2).sum()` and `d1 @ d2` should be consistent.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,549679475
https://github.com/pydata/xarray/issues/3694#issuecomment-574425136,https://api.github.com/repos/pydata/xarray/issues/3694,574425136,MDEyOklzc3VlQ29tbWVudDU3NDQyNTEzNg==,6815844,2020-01-14T23:37:11Z,2020-01-14T23:37:11Z,MEMBER,"I have no strong opinion, but if most of the arithmetic in xarray uses `join='inner'`, then it would be nicer to do so here too.


","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,549679475