issue_comments: 651674763

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https://github.com/pydata/xarray/issues/4186#issuecomment-651674763 https://api.github.com/repos/pydata/xarray/issues/4186 651674763 MDEyOklzc3VlQ29tbWVudDY1MTY3NDc2Mw== 15720911 2020-06-30T09:24:13Z 2020-06-30T09:24:13Z NONE

Hi @shoyer , without dataframe.set_index(), dataframe.index can potentially be different from idx returned by remove_unused_levels_categories, this will lead to other problems. One example is the following df: df = pd.DataFrame( { 'lev1': pd.Series( ['b', 'a'], dtype=pd.CategoricalDtype(['c', 'b', 'a'], ordered=True) ), 'lev2': 'foo', 'C1': [0, 2], 'C2': [1, 3], } ).set_index(['lev1', 'lev2'])

I agree it will be better if we can maintain the order from df to xr.Dataset, but I think we should never work with a copy of idx which is different from dataframe.index, as this will lead to hard to debug problems due to "surprising" behavior pandas does.

 
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