Description
MCVE Code Sample
>>> ds = xr.DataArray(np.ones((4,5)), dims=['z', 'x']).to_dataset(name='a')
>>> ds.a.groupby('z').mean()
<xarray.DataArray 'a' (z: 4)>
array([1., 1., 1., 1.])
Dimensions without coordinates: z
>>> ds.groupby('z').mean()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Users/noah/miniconda3/envs/broken/lib/python3.7/site-packages/xarray/core/common.py", line 91, in wrapped_func
**kwargs
File "/Users/noah/miniconda3/envs/broken/lib/python3.7/site-packages/xarray/core/groupby.py", line 848, in reduce
return self.apply(reduce_dataset)
File "/Users/noah/miniconda3/envs/broken/lib/python3.7/site-packages/xarray/core/groupby.py", line 796, in apply
return self._combine(applied)
File "/Users/noah/miniconda3/envs/broken/lib/python3.7/site-packages/xarray/core/groupby.py", line 800, in _combine
applied_example, applied = peek_at(applied)
File "/Users/noah/miniconda3/envs/broken/lib/python3.7/site-packages/xarray/core/utils.py", line 181, in peek_at
peek = next(gen)
File "/Users/noah/miniconda3/envs/broken/lib/python3.7/site-packages/xarray/core/groupby.py", line 795, in <genexpr>
applied = (func(ds, *args, **kwargs) for ds in self._iter_grouped())
File "/Users/noah/miniconda3/envs/broken/lib/python3.7/site-packages/xarray/core/groupby.py", line 846, in reduce_dataset
return ds.reduce(func, dim, keep_attrs, **kwargs)
File "/Users/noah/miniconda3/envs/broken/lib/python3.7/site-packages/xarray/core/dataset.py", line 3888, in reduce
"Dataset does not contain the dimensions: %s" % missing_dimensions
ValueError: Dataset does not contain the dimensions: ['z']
>>> ds.dims
Frozen(SortedKeysDict({'z': 4, 'x': 5}))Problem Description
Groupby reduction operations on Dataset objects no longer seem to work in xarray v0.13. In the example, above I create an xarray dataset with one dataarray called "a". The same groupby operations fails on this Dataset, but succeeds when called directly on "a". Is this a bug or an intended change?
In addition the error message is confusing since z is one of the Dataset dimensions.
Output of xr.show_versions()
INSTALLED VERSIONS
commit: None
python: 3.7.3 | packaged by conda-forge | (default, Jul 1 2019, 14:38:56)
[Clang 4.0.1 (tags/RELEASE_401/final)]
python-bits: 64
OS: Darwin
OS-release: 18.6.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8
libhdf5: None
libnetcdf: None
xarray: 0.13.0
pandas: 0.25.1
numpy: 1.17.2
scipy: None
netCDF4: None
pydap: None
h5netcdf: None
h5py: None
Nio: None
zarr: None
cftime: None
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: None
dask: None
distributed: None
matplotlib: None
cartopy: None
seaborn: None
numbagg: None
setuptools: 41.2.0
pip: 19.2.3
conda: None
pytest: None
IPython: None
sphinx: None