Problem when calculating a baseline using a constant number

[matteodefelice]

Mentioned in #49
It seems that a piece code that was working one year ago:

baseline = xs.brier_score(obs_final >  obs_final.quantile(2/3, dim = 'time'), 2/3)

doesn't work any more, I get this error on my Colab:

AttributeError                            Traceback (most recent call last)

<ipython-input-68-ad9dcdfd6ce1> in <module>()
----> 1 baseline = xs.brier_score(obs_final >  obs_final.quantile(2/3, dim = 'time'), 2/3)

/usr/local/lib/python3.8/site-packages/xskillscore/core/probabilistic.py in brier_score(observations, forecasts, member_dim, fair, dim, weights, keep_attrs)
    348                 res = (e / M - o) ** 2 - e * (M - e) / (M ** 2 * (M - 1))
    349         else:
--> 350             if member_dim in forecasts.dims:
    351                 forecasts = forecasts.mean(member_dim)
    352             res = xr.apply_ufunc(

AttributeError: 'float' object has no attribute 'dims'

The error is due to the fact that now in processing.py is checking dims in forecasts, throwing an error if that is not an xarray object.

[dougiesquire]

Thanks for reporting this @matteodefelice .

@aaronspring , do you know what the issue is here off the top of your head? And when was it introduced?

[aaronspring]

I see the problem quite straight-forward: xs expects xr.Datasets or xr.DataArrays. with PR #162 I added this check for member_dim in forecasts, which fails for a number. could be simply fixed by isinstance(forecast, number) meaning no member_dim

[matteodefelice]

Here

xskillscore/xskillscore/core/probabilistic.py

Line 350 in 4c6e5e1

if member_dim in forecasts.dims:

If forecasts is a float it has no attributes. I should try to use a DataArray containing a single value

[aaronspring]

exactly, should work

[bradyrx]

@aaronspring we might want to port over that small custom error code piece from climpred that defines DatasetError/DataArrayError to have more clean error reporting here.