pydata/pandas — pull request #7975 by jreback (2014-08-10 01:24:50+00:00)
Title: PERF: perf improvements for Series.transform (revised) (GH6496)

xref #6496

Additional perf improvements for Series.transform (when specifying cythonizable functions)

```
-------------------------------------------------------------------------------
Test name | head[ms] | base[ms] | ratio |
-------------------------------------------------------------------------------
groupby_transform_series2 | 98.7293 | 3621.1437 | 0.0273 |
groupby_transform2 | 19.5080 | 168.8046 | 0.1156 |
```