Allow passing of positional arguments in apply for Groupby objects

[maaleske]

• Closes Inconsistent signature of apply #2412
• Tests added (for all bug fixes or enhancements)
• Tests passed (for all non-documentation changes)
• Fully documented, including whats-new.rst for all changes and api.rst for new API

[shoyer]

Looks good to me, thanks!

For consistency, can you update the apply method on the classes in xarray/core/resample.py as well?

[shoyer]

This still needs tests, to verify that this argument works.

[maaleske]

I added tests for groupby. I haven't used resampling so I'm struggling a bit to make a sensible dataset/array for a similar test of the resample method.

[spencerkclark]

Thanks @maaleske -- following the style of your groupby tests, you could do something like this, e.g. for the DataArray case:

def test_da_resample_func_args():

    def func(arg1, arg2, arg3=0.):
        return arg1.mean('time') + arg2 + arg3

    times = pd.date_range('2000', periods=3, freq='D')
    da = xr.DataArray([1., 1., 1.], coords=[times], dims=['time'])
    expected = xr.DataArray([3., 3., 3.], coords=[times], dims=['time'])
    actual = da.resample(time='D').apply(func, args=(1,), arg3=1)
    assert_identical(actual, expected)

[maaleske]

Thanks @spencerkclark, I had almost the exact same code already written but couldn't figure out the return value resample.apply needs from func to work. I added the tests to test_dataarray and test_dataset, since there doesn't appear to be a separate file for resample (as there is for groupby).

[dcherian]

lgtm

[pep8speaks]

Hello @maaleske! Thanks for updating the PR.

Cheers ! There are no PEP8 issues in this Pull Request. 🍻

Comment last updated on December 24, 2018 at 17:50 Hours UTC

[shoyer]

Thanks!