issue_comments: 454981881

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https://github.com/pydata/xarray/issues/2685#issuecomment-454981881 https://api.github.com/repos/pydata/xarray/issues/2685 454981881 MDEyOklzc3VlQ29tbWVudDQ1NDk4MTg4MQ== 5635139 2019-01-16T23:20:34Z 2019-01-16T23:20:34Z MEMBER

Thanks for the report @lexual . Agree that's unclear:

The error message should state that you use apply since it's a lambda; e.g.

```python

fn = lambda x: xr.DataArray(3) da.resample(time='QS-DEC').apply(fn)

Out[19]: <xarray.DataArray (time: 4)> array([3, 3, 3, 3]) Coordinates: * time (time) datetime64[ns] 1999-12-01 2000-03-01 2000-06-01 2000-09-01 ```

We'd take a PR to fix that, but fairly low priority given it's a deprecated feature

But the function also fails for fn = lambda values: 3 (and fn = lambda x: x.sum().item()); I think we could add something to handle a function that returns a number rather than an array

 
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