Closed
Description
The documentation of SparseArray.cumsum
says it returns a Series
, but that is not the case:
>>> from pandas import SparseArray, np
>>> data = np.arange(10)
>>> s = SparseArray(data, fill_value=np.nan)
>>> type(s.cumsum())
<class 'pandas.sparse.array.SparseArray'>
>>>
>>> s = SparseArray(data, fill_value=2)
>>> type(s.cumsum())
<class 'numpy.ndarray'>
Given that to_dense
now returns self.values
and ignores fill_value
, this current behaviour in cumsum
seems illogical and should probably just return SparseArray
regardless. At the very least though, I think a documentation fix is in order.
EDIT: there is a similar issue with SparseSeries
that should also be addressed