issues: 2021858121

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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
2021858121 PR_kwDOAMm_X85g81wJ 8510 Grouper object design doc 2448579 closed 0     6 2023-12-02T04:56:54Z 2024-03-06T02:27:07Z 2024-03-06T02:27:04Z MEMBER   0 pydata/xarray/pulls/8510

xref #8509, #6610

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@pydata/xarray I've been poking at this on and off for a year now and finally figured out how to do it cleanly (#8509).

I wrote up a design doc for Grouper objects that allow custom conversion of DataArrays to integer group codes, following the NEP template (which is absolutely great!). Such Grouper objects allow us to generalize the GroupBy interface to a much larger class of problems, and eventually provide a nice path to grouping by multiple variables (#6610)

8509 implements two custom Groupers for you to try out :)

```python import xarray as xr from xarray.core.groupers import SeasonGrouper, SeasonResampler

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

custom seasons!

ds.air.groupby(time=SeasonGrouper(["JF", "MAM", "JJAS", "OND"])).mean()

ds.air.resample(time=SeasonResampler(["DJF", "MAM", "JJAS", "ON"])).count() ```

All comments are welcome, 1. there are a couple of specific API and design decisions to be made. I'll make some comments pointing these out. 2. I'm also curious about what Grouper objects we should provide in Xarray.

cc @ilan-gold @ivirshup @aulemahal @tomvothecoder @jbusecke @katiedagon - it would be good to hear what "Groupers" would be useful for your work / projects. I bet you already have examples that fit this proposal

 
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