xr.polyval: return nan when evaluating a curve with nan coefficients

[FRidh]

What happened?

Evaluating the coefficients from a polyfit that happened to be none results in a polyval evaluation of zeros.

What did you expect to happen?

I expect the result to be nan when an input is nan as well. Note passing in skipna=True to polyfit does not make a difference.

Minimal Complete Verifiable Example

import xarray as xr
import numpy as np
arr = xr.DataArray(np.ones(100)*np.nan, dims=["time"], coords={"time": np.arange(100)})
xr.polyval(arr.time, arr.polyfit(dim="time", deg=1))

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.

Relevant log output

No response

Anything else we need to know?

No response

Environment

: None seaborn: None numbagg: None fsspec: 2022.01.0 cupy: None pint: None sparse: None setuptools: 61.2.0.post0 pip: None conda: None pytest: 7.1.1 IPython: 8.2.0 sphinx: 4.5.0

[dcherian]

Fixed on main thanks to @headtr1ck !

[FRidh]

Ohh, great, thanks! I guess then it was #6601 that fixed this.