pydata/pandas — pull request #9007 by SteveSimmons (2014-12-05 00:24:42+00:00)
Title: Fix groupby().transform() example in cookbook.rst

@jorisvandenbossche : Fixes code in example, and makes final averaging by len(x) stylistically similar to previous adds.
New pull request replacing my earlier one, which contained some other erroneous commits.