Code Sample, a copy-pastable example if possible

# Your code here
import pandas as pd
import numpy as np

u=pd.DataFrame([np.nan]*5)
u.sum()

Problem description

It returns 0.0 but it is written in http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.sum.html. That it should (and it seems normal) return nan. "If an entire row/column is NA, the result will be NA"

Expected Output

It should return nan.

Output of pd.show_versions()

# Paste the output here pd.show_versions() here pandas: 0.18.1 nose: 1.3.7 pip: 8.1.2 setuptools: 27.2.0 Cython: 0.24.1 numpy: 1.11.1 scipy: 0.18.1 statsmodels: 0.6.1 xarray: None IPython: 5.1.0 sphinx: 1.4.6 patsy: 0.4.1 dateutil: 2.5.3 pytz: 2016.6.1 blosc: None bottleneck: 1.1.0 tables: 3.2.2 numexpr: 2.6.1 matplotlib: 1.5.3 openpyxl: 2.3.2 xlrd: 1.0.0 xlwt: 1.1.2 xlsxwriter: 0.9.3 lxml: 3.6.4 bs4: 4.5.1 html5lib: None httplib2: None apiclient: None sqlalchemy: 1.0.13 pymysql: None psycopg2: None jinja2: 2.8 boto: 2.42.0 pandas_datareader: None

Comment From: bashtage

Is bottleneck >= 1.0 installed? Bottleneck return 0.0 for all nan arrays.

Comment From: jreback

this is a dupe of #9422 (details show bottleneck 1.1)