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/2170#issuecomment-407159487,https://api.github.com/repos/pydata/xarray/issues/2170,407159487,MDEyOklzc3VlQ29tbWVudDQwNzE1OTQ4Nw==,7441788,2018-07-23T18:39:52Z,2018-07-23T18:39:52Z,CONTRIBUTOR,"I second this request.

The following may not be optimal, but seems to work for me as a `keepdims=True` version of `reduce()`:
```
    def dim_preserving_reduce(self, func, dim=None, axis=None, label=None, keep_attrs=False, **kwargs):
        if axis is not None:
            dim = np.take(self._obj.dims, axis, mode='wrap')
        dims = dim if isinstance(dim, (list, tuple)) else [dim]
        dims_coords = {dim: [lab] for dim, lab in zip(dims, (label if isinstance(label, list) else [label]))}
        return self._obj.reduce(func, dim=dims, keep_attrs=keep_attrs, **kwargs). \
            expand_dims(dims, axis=[self._obj.dims.index(dim) for dim in dims]). \
            assign_coords(**dims_coords)
```

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