小编Hei*_*org的帖子

我有以下数据集：

import datetime
import pandas as pd

df = pd.DataFrame({'PORTFOLIO': ['A', 'A', 'A', 'A','A', 'A', 'A', 'A','A', 'A','A', 'A', 'A', 'A'],
               'DATE': ['28-02-2018','31-03-2018','30-04-2018','31-05-2018','30-06-2018','31-07-2018','31-08-2018',
                        '30-09-2018','31-10-2018','30-11-2018','31-12-2018','31-01-2019','28-02-2019','05-03-2019'],
               'IRR': [.7, .8, .9, .4, .2, .3, .4, .9, .7, .8, .9, .4,.7, .8],
               })
df

   PORTFOLIO       DATE  IRR
0          A 2018-02-28  0.7
1          A 2018-03-31  0.8
2          A 2018-04-30  0.9
3          A 2018-05-31  0.4
4          A 2018-06-30  0.2
5          A 2018-07-31  0.3
6          A 2018-08-31  0.4
7          A 2018-09-30  0.9
8          A 2018-10-31  0.7
9 …