AllenDowney/ThinkStats2 — pull request #13 by henrystokeley (2014-12-23 03:57:45+00:00)
Title: Remove SettingWithCopyWarning from thinkstats2.py

Fix SettingWithCopyWarning given by thinkstats2.py by using df.loc[b, a] rather than chain indexing df[a][b] as documented at:
http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy