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/4885#issuecomment-788052130,https://api.github.com/repos/pydata/xarray/issues/4885,788052130,MDEyOklzc3VlQ29tbWVudDc4ODA1MjEzMA==,5637662,2021-03-01T15:47:52Z,2021-03-01T15:47:52Z,CONTRIBUTOR,"I tried this:
```diff
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -4701,7 +4701,9 @@ class Dataset(Mapping, ImplementsDatasetReduce, DataWithCoords):
                 if not reduce_dims:
                     variables[name] = var
             else:
-                if (
+                if not reduce_dims:
+                    variables[name] = var
+                elif (
                     not numeric_only
                     or np.issubdtype(var.dtype, np.number)
                     or (var.dtype == np.bool_)
```
which works great for mean - ""var"" stays an integer, as expected.

However, that breaks `ds.std` - which should be zero for ""var"", but isn't.
I guess that is ok for coords - as the assumption is that on coordinates the calculation is not done, but for data variables this is probably not ok.

```diff
--- a/xarray/core/duck_array_ops.py
+++ b/xarray/core/duck_array_ops.py
@@ -537,6 +537,11 @@ def mean(array, axis=None, skipna=None, **kwargs):
     dtypes""""""
     from .common import _contains_cftime_datetimes
 
+    # The mean over an empty axis shouldn't change the data
+    # See https://github.com/pydata/xarray/issues/4885
+    if not axis:
+        return array
+
     array = asarray(array)
     if array.dtype.kind in ""Mm"":
         offset = _datetime_nanmin(array)
```
I think it is best to change mean - which would work also for dataArrays.
This implies that mean does not convert to float64 - as the numpy version does, but I guess that should be fine.

Should I open a PR?","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,805389572