Do not reindex gridded Datasets during groupby
@@ -102,7 +102,7 @@ class DataConversion(object):
elif groupby and not isinstance(groupby, list):
groupby = [groupby]
- if new_type._1d:
+ if self._element.interface.gridded:
selected = self._element
else:
selected = self._element.reindex(groupby+kdims, vdims)
