id,node_id,number,state,locked,title,user,body,created_at,updated_at,closed_at,merged_at,merge_commit_sha,assignee,milestone,draft,head,base,author_association,auto_merge,repo,url,merged_by
106592251,MDExOlB1bGxSZXF1ZXN0MTA2NTkyMjUx,1272,closed,0,Groupby-like API for resampling,4992424,"This is a work-in-progress to resolve #1269. 

- [x] Basic functionality
- [x] Cleanly deprecate old API 
- [x] New test cases
- [x] Documentation / examples
- [x] ""What's new""

Openly welcome feedback/critiques on how I approached this. Subclassing `Data{Array/set}GroupBy` may not be the best way, but it would be easy enough to re-write the necessary helper functions (just `apply()`, I think) so that we do not need to inherit form them directly. Additional issues I'm working to resolve:

- [x] I tried make sure that calls using the old API won't break by refactoring the old logic to `_resample_immediately()`. This may not be the best approach!
- [x] Similarly, I copied all the original test cases and added the suffix `..._old_api`; these could trivially be placed into their related test cases for the new API.
- [x] BUG: **keep_attrs** is ignored when you call it on methods chained to `Dataset.resample()`. Oddly enough, if I hard-code **keep_attrs=True** inside `reduce_array()` in `DatasetResample::reduce` it works just fine. I haven't figured out where the kwarg is getting lost.
- [x] BUG: Some of the test cases (for instance, `test_resample_old_vs_new_api`) fail because the resampling by calling `self.groupby_cls` ends up not working - it crashes because the group sizes that get computed are not what it expects. Occurs with both new and old API",2017-02-16T19:04:07Z,2017-09-22T16:27:36Z,2017-09-22T16:27:35Z,2017-09-22T16:27:35Z,dc7d733bcc10ce935304d65d03124471661243a3,,2415632,0,5cfba57c9dec5546c8441bb286107e55d048584c,7611ed9b678c4004855856d2ec6dc6eb7ac59123,NONE,,13221727,https://github.com/pydata/xarray/pull/1272,
114680372,MDExOlB1bGxSZXF1ZXN0MTE0NjgwMzcy,1356,closed,0,Add DatetimeAccessor for accessing datetime fields via `.dt` attribute,4992424," - [x] Partially closes #358 
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master | flake8 --diff``
 - [x] whatsnew entry

This uses the `register_dataarray_accessor` to add attributes similar to those in pandas` timeseries which let the users quickly access datetime fields from an underlying array of datetime-like values. The referenced issue (#358) also asks about adding similar accessors for `.str`, but this is a more complex topic - I think a compelling use-case would help in figuring out what the critical functionality is

## Virtual time fields

Presumably this could be used to augment `Dataset._get_virtual_variable()`. A **season** field would need to be added as a special field to the accessor.",2017-04-06T19:48:19Z,2017-04-29T01:19:12Z,2017-04-29T01:18:59Z,2017-04-29T01:18:59Z,8f6a68e3f821689203bce2bce52b412e9fe70b5c,,,0,b2863139ec3bc437030a48ff33a54d68ca91b026,ab4ffee919d4abe9f6c0cf6399a5827c38b9eb5d,NONE,,13221727,https://github.com/pydata/xarray/pull/1356,