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
677773328,MDU6SXNzdWU2Nzc3NzMzMjg=,4338,Combining tiled data sets in xarray,56926399,closed,0,,,4,2020-08-12T15:12:39Z,2020-08-13T12:04:11Z,2020-08-12T22:50:33Z,NONE,,,,"I'm working on a project where I need to combine different sets of geographic image tiles into one large tile in Xarray. I am running into an issue. I've made a simplified example bellow.

```python
square1 = xr.DataArray(name=""box1"", data=np.random.randint(5, size=(3, 2)), coords=[(""x"", [0,1,2]),('y',[0,1])])
square2 = xr.DataArray(name=""box2"", data=np.random.randint(5, size=(3, 2)), coords=[(""x"", [2,3,4]),('y',[0,1])])
square3 = xr.DataArray(name=""box3"", data=np.random.randint(5, size=(3, 2)), coords=[(""x"", [0,1,2]),('y',[2,3])])
square4 = xr.DataArray(name=""box4"", data=np.random.randint(5, size=(3, 2)), coords=[(""x"", [2,3,4]),('y',[2,3])])

combineddata = xr.combine_by_coords([square1,square2,square3,square4])
```
I thought this is all you need to do it but I get this error

```python
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-57-fc5add80d55a> in <module>
----> 1 xr.combine_by_coords([square1,square2,square3,square4])

~/my-conda-envs/dem/lib/python3.8/site-packages/xarray/core/combine.py in combine_by_coords(datasets, compat, data_vars, coords, fill_value, join, combine_attrs)
    713 
    714     # Group by data vars
--> 715     sorted_datasets = sorted(datasets, key=vars_as_keys)
    716     grouped_by_vars = itertools.groupby(sorted_datasets, key=vars_as_keys)
    717 

~/my-conda-envs/dem/lib/python3.8/site-packages/xarray/core/combine.py in vars_as_keys(ds)
    502 
    503 def vars_as_keys(ds):
--> 504     return tuple(sorted(ds))
    505 
    506 

~/my-conda-envs/dem/lib/python3.8/site-packages/xarray/core/common.py in __bool__(self)
    118 
    119     def __bool__(self: Any) -> bool:
--> 120         return bool(self.values)
    121 
    122     def __float__(self: Any) -> float:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
```
I am not really sure why this is not working. ","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/4338/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue