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
514077742,MDU6SXNzdWU1MTQwNzc3NDI=,3458,Keep index dimension when selecting only a single coord,13770365,open,0,,,6,2019-10-29T17:02:29Z,2021-03-02T06:48:08Z,,NONE,,,,"#### MCVE Code Sample
<!-- In order for the maintainers to efficiently understand and prioritize issues, we ask you post a ""Minimal, Complete and Verifiable Example"" (MCVE): http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports -->

```python
# Your code here
import numpy as np
import xarray as xr

data = np.zeros((10, 4))
example_xr = xr.DataArray(data, coords=[range(10), [""idx0"", ""idx1"", ""idx2"", ""dim3""]], dims=[""rows"", ""cols""])

# desired behavior
subset = example_xr[:, 1:2]
subset.shape

# inclusive indexing means both idx1 and idx2 kept
subset_named1 = example_xr.loc[:, ""idx1"":""idx2""]
subset_named1.shape

# slicing behavior means that 2nd dimension is dropped
subset_named2 = example_xr.loc[:, ""idx1""]
subset_named2.shape
```

#### Expected Output
I'd like to be able to use named .loc indexing to select only a single named coord from one dimension, but not have that dimension collapse when subsetting. 

#### Problem Description
<!-- this should explain why the current behavior is a problem and why the expected output is a better solution -->

I looked, but wasn't able to find anything in the documentation about how to perform this same action using named coords. It works with integer-based slicing. 

#### Output of ``xr.show_versions()``
<details>
# Paste the output here xr.show_versions() here

</details>
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