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
1826978659,I_kwDOAMm_X85s5Xtj,8028,Setting datarrays with non-dimension coordinates errors,14371165,open,0,,,6,2023-07-28T19:20:31Z,2023-08-10T15:25:23Z,,MEMBER,,,,"### What happened?

I'm not sure if this is a bug or a feature but I was expecting this example to work since the new coord is just a slight rewrite of the original dimension coordinate:

```python
import xarray as xr

ds = xr.tutorial.open_dataset(""air_temperature"")

# Change the first time value:
ds[""air_new""] = ds.air.copy()
air_new_changed = ds.air_new[{""time"": 0}] * 3
ds.air_new.loc[air_new_changed.coords] = air_new_changed  # Works! :)

# Add a another coord along time axis and change 
# the first time value:
ds[""air_new""] = ds.air.copy().assign_coords(
    {""time_float"": ds.time.astype(float)}
)
air_new_changed = ds.air_new[{""time"": 0}] * 4
ds.air_new.loc[air_new_changed.coords] = air_new_changed  # Error! :(

Traceback (most recent call last):

  Cell In[25], line 5
    ds.air_new.loc[air_new_changed.coords] = air_new_changed

  File ~\AppData\Local\mambaforge\envs\jw\lib\site-packages\xarray\core\dataarray.py:222 in __setitem__
    dim_indexers = map_index_queries(self.data_array, key).dim_indexers

  File ~\AppData\Local\mambaforge\envs\jw\lib\site-packages\xarray\core\indexing.py:182 in map_index_queries
    grouped_indexers = group_indexers_by_index(obj, indexers, options)

  File ~\AppData\Local\mambaforge\envs\jw\lib\site-packages\xarray\core\indexing.py:144 in group_indexers_by_index
    raise KeyError(f""no index found for coordinate {key!r}"")

KeyError: ""no index found for coordinate 'time_float'""
```


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