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
524940277,MDU6SXNzdWU1MjQ5NDAyNzc=,3546,"loc API gives KeyError: ""not all values found in index""",8934026,open,0,,,4,2019-11-19T11:11:13Z,2019-11-19T15:22:12Z,,NONE,,,,"I am having issues with the loc API of xarray. I am trying to select data that satisfy a certain condition. Below should be a reproducible example:

    import xarray as xr
    ds = xr.tutorial.load_dataset('air_temperature')
    da = ds.air
    mask = 2.3e2*xr.ones_like(da[0,0])
    da[0,0].loc[da[0,0]<mask]

but this gives the following error:

    ---------------------------------------------------------------------------
    KeyError                                  Traceback (most recent call last)
    <ipython-input-238-75b6b6f544d4> in <module>
          1 da = ds.air
          2 mask = 2.3e2*xr.ones_like(da[0,0])
    ----> 3 da[0,0].loc[da[0,0]<mask]
    
    ~/miniconda3/envs/ensemble/lib/python3.7/site-packages/xarray/core/dataarray.py in __getitem__(self, key)
        194             labels = indexing.expanded_indexer(key, self.data_array.ndim)
        195             key = dict(zip(self.data_array.dims, labels))
    --> 196         return self.data_array.sel(**key)
        197 
        198     def __setitem__(self, key, value) -> None:
    
    ~/miniconda3/envs/ensemble/lib/python3.7/site-packages/xarray/core/dataarray.py in sel(self, indexers, method, tolerance, drop, **indexers_kwargs)
       1045             method=method,
       1046             tolerance=tolerance,
    -> 1047             **indexers_kwargs
       1048         )
       1049         return self._from_temp_dataset(ds)
    
    ~/miniconda3/envs/ensemble/lib/python3.7/site-packages/xarray/core/dataset.py in sel(self, indexers, method, tolerance, drop, **indexers_kwargs)
       1998         indexers = either_dict_or_kwargs(indexers, indexers_kwargs, ""sel"")
       1999         pos_indexers, new_indexes = remap_label_indexers(
    -> 2000             self, indexers=indexers, method=method, tolerance=tolerance
       2001         )
       2002         result = self.isel(indexers=pos_indexers, drop=drop)
    
    ~/miniconda3/envs/ensemble/lib/python3.7/site-packages/xarray/core/coordinates.py in remap_label_indexers(obj, indexers, method, tolerance, **indexers_kwargs)
        390 
        391     pos_indexers, new_indexes = indexing.remap_label_indexers(
    --> 392         obj, v_indexers, method=method, tolerance=tolerance
        393     )
        394     # attach indexer's coordinate to pos_indexers
    
    ~/miniconda3/envs/ensemble/lib/python3.7/site-packages/xarray/core/indexing.py in remap_label_indexers(data_obj, indexers, method, tolerance)
        259             coords_dtype = data_obj.coords[dim].dtype
        260             label = maybe_cast_to_coords_dtype(label, coords_dtype)
    --> 261             idxr, new_idx = convert_label_indexer(index, label, dim, method, tolerance)
        262             pos_indexers[dim] = idxr
        263             if new_idx is not None:
    
    ~/miniconda3/envs/ensemble/lib/python3.7/site-packages/xarray/core/indexing.py in convert_label_indexer(index, label, index_name, method, tolerance)
        191             indexer = get_indexer_nd(index, label, method, tolerance)
        192             if np.any(indexer < 0):
    --> 193                 raise KeyError(""not all values found in index %r"" % index_name)
        194     return indexer, new_index
        195 
    
    KeyError: ""not all values found in index 'lat'""

Since the `mask` is identical to the xarray.DataArray `da` in terms of dimensions and coordinates, I don't think this error makes sense... If I change the coordinates in the following manner:

```
da = xr.DataArray(ds.air.data, dims=ds.air.dims, 
                  coords={'time':range(len(ds.time)),'lat':range(len(ds.lat)),'lon':range(len(ds.lon))})
mask = da[0,0] < 2.3e2*xr.ones_like(da[0,0])
da[0,0].loc[mask]
```

it works:

```
<xarray.DataArray (lon: 5)>
array([228.79999, 227.29999, 227.     , 227.5    , 228.79999],
      dtype=float32)
Coordinates:
    time     int64 0
    lat      int64 0
  * lon      (lon) int64 44 45 46 47 48
```

Am I missing something or is this possibly a bug? Thank you in advance for your help.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3546/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue