issues: 1217543476

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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
1217543476 I_kwDOAMm_X85Ikj00 6526 xr.polyval first arg requires name attribute 43316012 closed 0     2 2022-04-27T15:47:02Z 2022-05-05T19:15:58Z 2022-05-05T19:15:58Z COLLABORATOR      

What happened?

I have some polynomial coefficients and want to evaluate them at some values using xr.polyval.

As described in the docstring/docu I created a 1D coordinate DataArray and pass it to xr.polyval but it raises a KeyError (see example).

What did you expect to happen?

I expected that the polynomial would be evaluated at the given points.

Minimal Complete Verifiable Example

```Python import xarray as xr

coeffs = xr.DataArray([1, 2, 3], dims="degree")

With a "handmade" coordinate it fails:

coord = xr.DataArray([0, 1, 2], dims="x")

xr.polyval(coord, coeffs)

raises:

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "xarray/core/computation.py", line 1847, in polyval

x = get_clean_interp_index(coord, coord.name, strict=False)

File "xarray/core/missing.py", line 252, in get_clean_interp_index

index = arr.get_index(dim)

File "xarray/core/common.py", line 404, in get_index

raise KeyError(key)

KeyError: None

If one adds a name to the coord that is called like the dimension:

coord2 = xr.DataArray([0, 1, 2], dims="x", name="x")

xr.polyval(coord2, coeffs)

works

```

Relevant log output

No response

Anything else we need to know?

I assume that the "standard" workflow is to obtain the coord argument from an existing DataArrays coordinate, where the name would be correctly set already. However, that is not clear from the description, and also prevents my "manual" workflow.

It could be that the problem will be solved by replacing the coord DataArray argument by an explicit Index in the future.

Environment

INSTALLED VERSIONS ------------------ commit: None python: 3.9.10 (main, Mar 15 2022, 15:56:56) [GCC 7.5.0] python-bits: 64 OS: Linux OS-release: 3.10.0-1160.49.1.el7.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: ('en_US', 'UTF-8') libhdf5: 1.12.0 libnetcdf: 4.7.4 xarray: 2022.3.0 pandas: 1.4.2 numpy: 1.22.3 scipy: None netCDF4: 1.5.8 pydap: None h5netcdf: None h5py: None Nio: None zarr: None cftime: 1.6.0 nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: None dask: None distributed: None matplotlib: 3.5.1 cartopy: 0.20.2 seaborn: None numbagg: None fsspec: None cupy: None pint: None sparse: None setuptools: 58.1.0 pip: 22.0.4 conda: None pytest: None IPython: 8.2.0 sphinx: None 
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   completed 13221727 issue

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