It is not possible to perform trivial operations like standardization of data e.g.

ddf = (ddf - ddf.mean(axis=0))  /  ddf.std(axis=0)

It throws an error saying

ValueError: Not all divisions are known, can't align partitions. 
Please use `set_index` or `set_partition` to set the index.

The output of the reduction operations are Series with one row and same number of columns so it shouldn't need to know the divisions. However, would it make sense to set the divisions of the Series to be the start and end divisions of the DataFrame that was reduced?