issue_comments: 388489805

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https://github.com/pydata/xarray/issues/2113#issuecomment-388489805 https://api.github.com/repos/pydata/xarray/issues/2113 388489805 MDEyOklzc3VlQ29tbWVudDM4ODQ4OTgwNQ== 17162724 2018-05-11T21:25:32Z 2018-05-11T21:25:50Z CONTRIBUTOR

I realized there with an issue before that in without center=True it doesn't raise an issue but it returns rubbish:

``` import xarray as xr import numpy as np

a = xr.DataArray(np.arange(1,4), coords=[np.arange(1,4)], dims='x') print(a.rolling(x=3, center=True).mean()) Out[2]: <xarray.DataArray (x: 3)> array([ nan, 2., nan]) Coordinates: * x (x) int64 1 2 3 print(a.chunk().rolling(x=3).mean().values) Out[3]: array([ -6.14891469e+18, -9.22337204e+18, -1.22978294e+19]) ```

The culprit lies in a dask function https://github.com/pydata/xarray/blob/6d8ac11ca0a785a6fe176eeca9b735c321a35527/xarray/core/dask_array_ops.py#L24

Not sure if this is an issue with the function or the way the data is going into the function.

For the center=True issue: https://github.com/pydata/xarray/blob/6d8ac11ca0a785a6fe176eeca9b735c321a35527/xarray/core/rolling.py#L308 is slicing the data.

 
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