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/4995#issuecomment-799047819,https://api.github.com/repos/pydata/xarray/issues/4995,799047819,MDEyOklzc3VlQ29tbWVudDc5OTA0NzgxOQ==,43613877,2021-03-15T02:28:51Z,2021-03-15T02:28:51Z,CONTRIBUTOR,"Thanks @dcherian, this is doing the job. I'll close this issue as there seems to be no need to implement this into the `sel` method.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,822320976
https://github.com/pydata/xarray/issues/4995#issuecomment-791019238,https://api.github.com/repos/pydata/xarray/issues/4995,791019238,MDEyOklzc3VlQ29tbWVudDc5MTAxOTIzOA==,43613877,2021-03-04T23:10:11Z,2021-03-04T23:10:11Z,CONTRIBUTOR,"Introducing a `fill_value` seems like a good idea, such that the size of the output does not change compared to the intended selection.
Choosing the original/requested coordinate as a label for the missing datapoint seems to be a valid choice because this position has been checked for valid data nearby without success.
I would suggest, that the `fill_value` should then be automatically determined from the `_FillValue`, the datatype and only at last requires the `fill_value` to be set.

However, the shortcoming that I see in using a `fill_value` is that the indexing has to modify the data ( insert e.g. `-999`) and also 'invent' a new coordinate point ( here `40`). This gets reasonably complex, when applying to a dataset with DataArrays of different types, e.g.
```python
import numpy as np
import xarray as xr

ds = xr.Dataset()
ds['data1'] = xr.DataArray(np.array([1,2,3,4,5], dtype=int), dims=[""lat""], coords={'lat':[10,20,30,50,60]})
ds['data2'] = xr.DataArray(np.array([1,2,3,4,5], dtype=float), dims=[""lat""], coords={'lat':[10,20,30,50,60]})
```
One `fill_value` might not fit to all data arrays being it because of the datatype or the actual data. E.g. `-999` might be a good `fill_value` for one DataArray but a valid datapoint in another one.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,822320976