pydata/pandas — pull request #7881 by jreback (2014-07-30 16:50:51+00:00)
Title: PERF: groupby / frame apply optimization

```
-------------------------------------------------------------------------------
Test name | head[ms] | base[ms] | ratio |
-------------------------------------------------------------------------------
groupby_frame_apply_overhead | 9.1400 | 70.3743 | 0.1299 |
groupby_frame_apply | 43.5640 | 186.6427 | 0.2334 |
groupby_apply_dict_return | 39.6016 | 80.1926 | 0.4938 |
```