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 340316108,MDU6SXNzdWUzNDAzMTYxMDg=,2280,string coords are converted to object dtype when using MultiIndex / stacking,1034035,closed,0,,,5,2018-07-11T16:26:12Z,2022-09-27T12:12:06Z,2022-09-27T12:12:05Z,NONE,,,,"#### Code Sample ```python import xarray as xr import pandas as pd indx = pd.MultiIndex.from_arrays([['1', '2', '1', '2'], ['100', '100', '200', '200']], names=['a', 'b']) # MultiIndex(levels=[['1', '2'], ['100', '200']], # labels=[[0, 1, 0, 1], [0, 0, 1, 1]], # names=['a', 'b']) tst = xr.DataArray(data=np.random.random((4)), coords=[('ab', indx)]) # # array([0.754308, 0.268363, 0.799407, 0.513185]) # Coordinates: # * ab (ab) MultiIndex # - a (ab) object '1' '2' '1' '2' # - b (ab) object '100' '100' '200' '200' tst2 = xr.DataArray(data=np.random.random((2,2)), coords=[('a', ['1', '2']), ('b', ['100', '200'])]) # # array([[0.854303, 0.179755], # [0.463453, 0.478913]]) # Coordinates: # * a (a) # array([0.854303, 0.179755, 0.463453, 0.478913]) # Coordinates: # * ab (ab) MultiIndex # - a (ab) object '1' '1' '2' '2' # - b (ab) object '100' '200' '100' '200' ``` #### Problem description The dtype for `a` and `b` in `tst` and `tst2.stack()` is `object` rather than some string dtype. #### Expected Output A string dtype for `a` and `b`. #### Output of ``xr.show_versions()``
# Paste the output here xr.show_versions() here INSTALLED VERSIONS ------------------ commit: None python: 3.6.5.final.0 python-bits: 64 OS: Linux OS-release: 4.15.0-24-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 xarray: 0.10.7 pandas: 0.23.1 numpy: 1.14.5 scipy: 1.1.0 netCDF4: 1.4.0 h5netcdf: 0.6.1 h5py: 2.8.0 Nio: None zarr: None bottleneck: 1.2.1 cyordereddict: None dask: 0.18.1 distributed: 1.22.0 matplotlib: 2.2.2 cartopy: None seaborn: 0.8.1 setuptools: 39.2.0 pip: 9.0.3 conda: 4.5.5 pytest: 3.6.2 IPython: 6.4.0 sphinx: 1.7.5
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