issues: 1325665237

What happened?

To note, I'm using the stable version(2022.6.0).

First, I'm confused that both dimension coordinate/non-dimension coordinate and index coordinate/non-index coordinate appear in the documentation(search to see), but they seem to be the same thing.

Second, I found that there are some errors in the documentation:

• It says that "The index associated with dimension name x can be retrieved by arr.indexes[x]. By construction, len(arr.dims) == len(arr.indexes)", which is inconsistent with actual behavior. See example code below: ```python In [0]: import xarray as xr, numpy as np In [1]: arr = xr.DataArray(np.zeros((2, 3)), dims=['x', 'y'], coords={'x': ['a', 'b']}) In [2]: assert len(arr.dims) == len(arr.indexes), f"{len(arr.dims)=}, {len(arr.indexes)=}"

---

AssertionError Traceback (most recent call last) <ipython-input-202-f217d18e6979> in <module> ----> 1 assert len(arr.dims) == len(arr.indexes), f"{len(arr.dims)=}, {len(arr.indexes)=}"

AssertionError: len(arr.dims)=2, len(arr.indexes)=1 In [3]: arr.indexes Out[3]: Indexes: x: Index(['a', 'b'], dtype='object', name='x') It seems that `arr.indexes` only returns indexes of dimensions that have coordinates. However, it's possible to get the index of dimension `y` through `get_index()`:python In [4]: arr.get_index('y') Out[4]: RangeIndex(start=0, stop=3, step=1, name='y') ```

• It says that: (see link)

For convenience multi-index levels are directly accessible as “virtual” or “derived” coordinates (marked by - when printing a dataset or data array): ```python In [77]: mda["band"] Out[77]: <xarray.DataArray 'band' (spec: 4)> array(['R', 'R', 'V', 'V'], dtype=object) Coordinates: * spec (spec) object MultiIndex * band (spec) object 'R' 'R' 'V' 'V' * wn (spec) float64 0.1 0.2 0.7 0.9

In [78]: mda.wn Out[78]: <xarray.DataArray 'wn' (spec: 4)> array([0.1, 0.2, 0.7, 0.9]) Coordinates: * spec (spec) object MultiIndex * band (spec) object 'R' 'R' 'V' 'V' * wn (spec) float64 0.1 0.2 0.7 0.9 `` As you can see, even in the given example code offered by the offical, all the "virtual" coordinates are marked as*instead of-`, which is a little bit confusing when handling multi-index coordinates in my experience.

May I have missed something? Thanks in advance for the reply.

What did you expect to happen?

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Minimal Complete Verifiable Example

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MVCE confirmation

• [ ] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• [ ] Complete example — the example is self-contained, including all data and the text of any traceback.
• [ ] Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• [ ] New issue — a search of GitHub Issues suggests this is not a duplicate.

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Anything else we need to know?

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Environment

INSTALLED VERSIONS ------------------ commit: None python: 3.8.10 (default, Sep 28 2021, 16:10:42) [GCC 9.3.0] python-bits: 64 OS: Linux OS-release: 5.10.102.1-microsoft-standard-WSL2 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: C.UTF-8 LOCALE: ('en_US', 'UTF-8') libhdf5: None libnetcdf: None xarray: 2022.6.0 pandas: 1.4.3 numpy: 1.23.1 scipy: 1.3.3 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: 3.1.2 cartopy: None seaborn: None numbagg: None fsspec: None cupy: None pint: None sparse: None flox: None numpy_groupies: None setuptools: 45.2.0 pip: 22.2.1 conda: None pytest: None IPython: 7.13.0 sphinx: None