html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/issues/6597#issuecomment-1124863541,https://api.github.com/repos/pydata/xarray/issues/6597,1124863541,IC_kwDOAMm_X85DDA41,22245117,2022-05-12T11:12:39Z,2022-05-12T11:12:39Z,CONTRIBUTOR,"Thanks - I think I might be misunderstanding how the new implementation works.
I tried the following changes, but both of them return an error:
```python
xr.polyval(values - values[0], polyfit_coefficients)
```
```
Traceback (most recent call last):
File ""/Users/mattia/MyGit/test.py"", line 31, in
xr.polyval(values - values[0], polyfit_coefficients)
File ""/Users/mattia/MyGit/xarray/xarray/core/computation.py"", line 1908, in polyval
coord = _ensure_numeric(coord) # type: ignore # https://github.com/python/mypy/issues/1533 ?
File ""/Users/mattia/MyGit/xarray/xarray/core/computation.py"", line 1949, in _ensure_numeric
return to_floatable(data)
File ""/Users/mattia/MyGit/xarray/xarray/core/computation.py"", line 1939, in to_floatable
x.data,
ValueError: cannot include dtype 'm' in a buffer
```
```python
xr.polyval(azimuth_time.coords[""azimuth_time""], polyfit_coefficients)
```
```
Traceback (most recent call last):
File ""/Users/mattia/MyGit/test.py"", line 31, in
xr.polyval(azimuth_time.coords[""azimuth_time""], polyfit_coefficients)
File ""/Users/mattia/MyGit/xarray/xarray/core/computation.py"", line 1908, in polyval
coord = _ensure_numeric(coord) # type: ignore # https://github.com/python/mypy/issues/1533 ?
File ""/Users/mattia/MyGit/xarray/xarray/core/computation.py"", line 1949, in _ensure_numeric
return to_floatable(data)
File ""/Users/mattia/MyGit/xarray/xarray/core/computation.py"", line 1938, in to_floatable
data=datetime_to_numeric(
File ""/Users/mattia/MyGit/xarray/xarray/core/duck_array_ops.py"", line 434, in datetime_to_numeric
array = array - offset
numpy.core._exceptions._UFuncBinaryResolutionError: ufunc 'subtract' cannot use operands with types dtype('