issues: 728893769

Is your feature request related to a problem? Please describe.

Currently xarray objects containting datetimes don't operate with pandas' offset objects:

python times = pd.date_range("2000-01-01", freq="6H", periods=10) ds = xr.Dataset( { "foo": (["time", "x", "y"], np.random.randn(10, 5, 3)), "bar": ("time", np.random.randn(10), {"meta": "data"}), "time": times, } ) ds.attrs["dsmeta"] = "dsdata" ds.resample(time="24H").mean("time").time + to_offset("8H")

raises: ```

---

TypeError Traceback (most recent call last) <ipython-input-29-f9de46fe6c54> in <module> ----> 1 ds.resample(time="24H").mean("time").time + to_offset("8H")

/usr/local/lib/python3.8/site-packages/xarray/core/dataarray.py in func(self, other) 2763 2764 variable = ( -> 2765 f(self.variable, other_variable) 2766 if not reflexive 2767 else f(other_variable, self.variable)

/usr/local/lib/python3.8/site-packages/xarray/core/variable.py in func(self, other) 2128 with np.errstate(all="ignore"): 2129 new_data = ( -> 2130 f(self_data, other_data) 2131 if not reflexive 2132 else f(other_data, self_data)

TypeError: unsupported operand type(s) for +: 'numpy.ndarray' and 'pandas._libs.tslibs.offsets.Hour' ```

This is an issue because pandas resampling has deprecated loffset — from our test suite:

``` xarray/tests/test_dataset.py::TestDataset::test_resample_loffset /Users/maximilian/workspace/xarray/xarray/tests/test_dataset.py:3844: FutureWarning: 'loffset' in .resample() and in Grouper() is deprecated.

df.resample(freq="3s", loffset="8H")

becomes:

from pandas.tseries.frequencies import to_offset df = df.resample(freq="3s").mean() df.index = df.index.to_timestamp() + to_offset("8H")

ds.bar.to_series().resample("24H", loffset="-12H").mean()

```

...and so we'll need to support something like this in order to maintain existing behavior.

Describe the solution you'd like I'm not completely sure; I think probably supporting the operations between xarray objects containing datetime objects and pandas' offset objects.