issue_comments: 761907785

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https://github.com/pydata/xarray/pull/4108#issuecomment-761907785 https://api.github.com/repos/pydata/xarray/issues/4108 761907785 MDEyOklzc3VlQ29tbWVudDc2MTkwNzc4NQ== 14808389 2021-01-18T00:22:57Z 2021-01-18T00:23:50Z MEMBER

I wonder if it would be better to first "reorganize" all of the existing functions: we currently have rename (and Dataset.rename_dims / Dataset.rename_vars), set_coords, reset_coords, set_index, reset_index and swap_dims, which overlap partially. For example, the code sample from #4417 works if instead of python ds = ds.rename(b='x') ds = ds.set_coords('x') we use python ds = ds.set_index(x="b") and something similar for the code sample in #4107.

I believe we currently have these use cases (not sure if that list is complete, though): - rename a DataArray → rename - rename a existing variable to a name that is not yet in the object → rename / Dataset.rename_vars / Dataset.rename_dirs - convert a data variable to a coordinate (not a dimension coordinate) → set_coords - convert a coordinate (not a dimension coordinate) to a data variable → reset_coords - swap a existing dimension coordinate with a coordinate (which may not exist) and rename the dimension → swap_dims - use a existing coordinate / data variable as a dimension coordinate (do not rename the dimension) → set_index - stop using a coordinate as dimension coordinate and append _ to its name (do not rename the dimension) → reset_index - use two existing coordinates / data variables as a MultiIndex → set_index - stop using a MultiIndex as a dimension coordinate and use its levels as coordinates → reset_index

Sometimes, some of these can be emulated by combinations of others, for example: ```python

x is a dimension without coordinates

assert_identical(ds.set_index({"x": "b"}), ds.swap_dims({"x": "b"}).rename({"b": "x"})) assert_identical(ds.swap_dims({"x": "b"}), ds.set_index({"x": "b"}).rename({"x": "b"})) and, with this PR:python assert_identical(ds.set_index({"x": "b"}), ds.set_coords("b").rename({"b": "x"})) assert_identical(ds.swap_dims({"x": "b"}), ds.rename({"b": "x"})) `` which means that it would increase the overlap ofrename,set_index, andswap_dims`.

In any case I think we should add a guide which explains which method to pick in which situation (or extend howdoi).

 
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