issues: 547091670

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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
547091670 MDU6SXNzdWU1NDcwOTE2NzA= 3674 Multi-index with categorical values 31126826 closed 0     7 2020-01-08T20:43:04Z 2020-03-13T19:55:07Z 2020-03-13T19:55:07Z CONTRIBUTOR      

Building a dataset from pandas with a multi-index with categorical values: ```python import pandas as pd

cat = pd.CategoricalDtype(categories=['foo', 'bar', 'baz']) i1 = pd.Series(['foo', 'bar'], dtype=cat) i2 = pd.Series(['bar', 'bar'], dtype=cat)

df = pd.DataFrame({'i1': i1, 'i2': i2, 'values': [1, 2]}) ds = df.set_index(['i1', 'i2']).to_xarray()

print(ds) ```

Expected output: <xarray.Dataset> Dimensions: (i1: 2, i2: 1) Coordinates: * i1 (i1) object 'foo' 'bar' * i2 (i2) object 'bar' Data variables: values (i1, i2) int64 1 2

Actual output: <xarray.Dataset> Dimensions: (i1: 3, i2: 3) Coordinates: * i1 (i1) object 'foo' 'bar' 'baz' * i2 (i2) object 'foo' 'bar' 'baz' Data variables: values (i1, i2) float64 nan 1.0 nan nan 2.0 nan nan nan nan

It is not wrong, but it is inconsistent with the non-categorical case (which gives the expected output above) and the single-index case (no filling with NaNs for single index).

Output of xr.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 3.8.0 (default, Nov 6 2019, 21:49:08) [GCC 7.3.0] python-bits: 64 OS: Linux OS-release: 4.19.91-1-MANJARO machine: x86_64 processor: byteorder: little LC_ALL: None LANG: fr_FR.UTF-8 LOCALE: fr_FR.UTF-8 libhdf5: None libnetcdf: None xarray: 0.14.1 pandas: 0.25.3 numpy: 1.17.4 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: 44.0.0.post20200106 pip: 19.3.1 conda: None pytest: None IPython: None sphinx: None 
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