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
638947370,MDU6SXNzdWU2Mzg5NDczNzA=,4156,writing sparse to netCDF,2448579,open,0,,,7,2020-06-15T15:33:23Z,2024-01-09T10:14:00Z,,MEMBER,,,,"I haven't looked at this too closely but it appears that this is a way to save MultiIndexed datasets to netCDF. So we may be able to do `sparse -> multiindex -> netCDF`

http://cfconventions.org/Data/cf-conventions/cf-conventions-1.8/cf-conventions.html#compression-by-gathering

cc @fujiisoup ","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/4156/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue
1916012703,I_kwDOAMm_X85yNAif,8239,Address repo-review suggestions,2448579,open,0,,,7,2023-09-27T17:18:40Z,2023-10-02T20:24:34Z,,MEMBER,,,,"### What is your issue?

Here's the output from the Scientific Python [Repo Review](https://repo-review.readthedocs.io/) tool.

There's an online version [here](https://learn.scientific-python.org/development/guides/repo-review/?repo=pydata%2Fxarray&branch=main).

On mac I run 
```
pipx run 'sp-repo-review[cli]' --format html --show err gh:pydata/xarray@main | pbcopy
```

A lot of these seem fairly easy to fix. I'll note that there's a large number of `mypy` config suggestions.

<h3>General</h3>
<ul>
<li>Detected build backend: <code>setuptools.build_meta</code></li>
<li>Detected license(s): Apache Software License</li>
</ul>
<table>
<tr><th>?</th><th>Name</th><th>Description</th></tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PY007</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/tasks#PY007"">Supports an easy task runner (nox or tox)</a>
<br/>
<p>Projects must have a <code>noxfile.py</code> or <code>tox.ini</code> to encourage new contributors.</p>

</td>
</tr>
</table>
<h3>PyProject</h3>

See https://github.com/pydata/xarray/issues/8239#issuecomment-1739363809

<table>
<tr><th>?</th><th>Name</th><th>Description</th></tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PP305</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/pytest#PP305"">Specifies xfail_strict</a>
<br/>
<p><code>xfail_strict</code> should be set. You can manually specify if a check
should be strict when setting each xfail.</p>
<pre><code class=""language-toml"">[tool.pytest.ini_options]
xfail_strict = true
</code></pre>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PP308</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/pytest#PP308"">Specifies useful pytest summary</a>
<br/>
<p><code>-ra</code> should be in <code>addopts = [...]</code> (print summary of all fails/errors).</p>
<pre><code class=""language-toml"">[tool.pytest.ini_options]
addops = [&quot;-ra&quot;, &quot;--strict-config&quot;, &quot;--strict-markers&quot;]
</code></pre>

</td>
</tr>
</table>
<h3>Pre-commit</h3>
<table>
<tr><th>?</th><th>Name</th><th>Description</th></tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PC110</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#PC110"">Uses black</a>
<br/>
<p>Use <code>https://github.com/psf/black-pre-commit-mirror</code> instead of <code>https://github.com/psf/black</code> in <code>.pre-commit-config.yaml</code></p>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PC160</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#PC160"">Uses codespell</a>
<br/>
<p>Must have <code>https://github.com/codespell-project/codespell</code> repo in <code>.pre-commit-config.yaml</code></p>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PC170</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#PC170"">Uses PyGrep hooks (only needed if RST present)</a>
<br/>
<p>Must have <code>https://github.com/pre-commit/pygrep-hooks</code> repo in <code>.pre-commit-config.yaml</code></p>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PC180</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#PC180"">Uses prettier</a>
<br/>
<p>Must have <code>https://github.com/pre-commit/mirrors-prettier</code> repo in <code>.pre-commit-config.yaml</code></p>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PC191</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#PC191"">Ruff show fixes if fixes enabled</a>
<br/>
<p>If <code>--fix</code> is present, <code>--show-fixes</code> must be too.</p>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>PC901</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#PC901"">Custom pre-commit CI message</a>
<br/>
<p>Should have something like this in <code>.pre-commit-config.yaml</code>:</p>
<pre><code class=""language-yaml"">ci:
  autoupdate_commit_msg: 'chore: update pre-commit hooks'
</code></pre>

</td>
</tr>
</table>
<h3>MyPy</h3>
<table>
<tr><th>?</th><th>Name</th><th>Description</th></tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>MY101</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#MY101"">MyPy strict mode</a>
<br/>
<p>Must have <code>strict</code> in the mypy config. MyPy is best with strict or
nearly strict configuration. If you are happy with the strictness of
your settings already, ignore this check or set <code>strict = false</code>
explicitly.</p>
<pre><code class=""language-toml"">[tool.mypy]
strict = true
</code></pre>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>MY103</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#MY103"">MyPy warn unreachable</a>
<br/>
<p>Must have <code>warn_unreachable = true</code> to pass this check. There are
occasionally false positives (often due to platform or Python version
static checks), so it's okay to ignore this check. But try it first - it
can catch real bugs too.</p>
<pre><code class=""language-toml"">[tool.mypy]
warn_unreachable = true
</code></pre>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>MY104</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#MY104"">MyPy enables ignore-without-code</a>
<br/>
<p>Must have <code>&quot;ignore-without-code&quot;</code> in <code>enable_error_code = [...]</code>. This
will force all skips in your project to include the error code, which
makes them more readable, and avoids skipping something unintended.</p>
<pre><code class=""language-toml"">[tool.mypy]
enable_error_code = [&quot;ignore-without-code&quot;, &quot;redundant-expr&quot;, &quot;truthy-bool&quot;]
</code></pre>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>MY105</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#MY105"">MyPy enables redundant-expr</a>
<br/>
<p>Must have <code>&quot;redundant-expr&quot;</code> in <code>enable_error_code = [...]</code>. This helps
catch useless lines of code, like checking the same condition twice.</p>
<pre><code class=""language-toml"">[tool.mypy]
enable_error_code = [&quot;ignore-without-code&quot;, &quot;redundant-expr&quot;, &quot;truthy-bool&quot;]
</code></pre>

</td>
</tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>MY106</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#MY106"">MyPy enables truthy-bool</a>
<br/>
<p>Must have <code>&quot;truthy-bool&quot;</code> in <code>enable_error_code = []</code>. This catches
mistakes in using a value as truthy if it cannot be falsey.</p>
<pre><code class=""language-toml"">[tool.mypy]
enable_error_code = [&quot;ignore-without-code&quot;, &quot;redundant-expr&quot;, &quot;truthy-bool&quot;]
</code></pre>

</td>
</tr>
</table>
<h3>Ruff</h3>
<table>
<tr><th>?</th><th>Name</th><th>Description</th></tr>
<tr style=""color: red;"">
<td><span role=""img"" aria-label=""Failed"">&#10060;</span></td>
<td>RF101</td>
<td>
<a href=""https://learn.scientific-python.org/development/guides/style#RF101"">Bugbear must be selected</a>
<br/>
<p>Must select the flake8-bugbear <code>B</code> checks. Recommended:</p>
<pre><code class=""language-toml"">[tool.ruff]
select = [
  &quot;B&quot;,  # flake8-bugbear
]
</code></pre>

</td>
</tr>
</table>



","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/8239/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue
540451721,MDExOlB1bGxSZXF1ZXN0MzU1MjU4NjMy,3646,[WIP] GroupBy plotting,2448579,open,0,,,7,2019-12-19T17:26:39Z,2022-06-09T14:50:17Z,,MEMBER,,1,pydata/xarray/pulls/3646,"<!-- Feel free to remove check-list items aren't relevant to your change -->

 - [x] Tests added
 - [x] Passes `black . && mypy . && flake8`
 - [ ] Fully documented, including `whats-new.rst` for all changes and `api.rst` for new API

This adds plotting methods to GroupBy objects so that it's easy to plot each group as a facet. I'm finding this super helpful in my current research project. 

It's pretty self-contained, mostly just adding `map_groupby*` methods to `FacetGrid`. But that's because I make `GroupBy` mimic the underlying `DataArray` by adding `coords`, `attrs` and `__getitem__`. 

This still needs more tests but I would like feedback on the feature and the implementation.

## Example

``` python
import numpy as np
import xarray as xr

time = np.arange(80)
da = xr.DataArray(5 * np.sin(2*np.pi*time/10), coords={""time"": time}, dims=""time"")
da[""period""] = da.time.where((time % 10) == 0).ffill(""time"")/10
da.plot()
```
![image](https://user-images.githubusercontent.com/2448579/71194665-49f45c00-2284-11ea-96e5-9a5daec1b3a9.png)

``` python
da.groupby(""period"").plot(col=""period"", col_wrap=4)
```
![image](https://user-images.githubusercontent.com/2448579/107123905-a1290780-685d-11eb-9bae-831a7513aaed.png)


``` python
da = da.expand_dims(y=10)
da.groupby(""period"").plot(col=""period"", col_wrap=4, sharex=False, sharey=True, robust=True)
```
![image](https://user-images.githubusercontent.com/2448579/71194716-5c6e9580-2284-11ea-832a-c4e7d9296390.png)

","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3646/reactions"", ""total_count"": 3, ""+1"": 2, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 1, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull