基于所有先前日期而不是按日期排序的先前行的滚动总和

Question

给定以下数据框：

+------------+--------+
|    Date    | Amount |
+------------+--------+
| 01/05/2019 |     15 |
| 27/05/2019 |     20 |
| 27/05/2019 |     15 |
| 25/06/2019 |     10 |
| 29/06/2019 |     25 |
| 01/07/2019 |     50 |
+------------+--------+

我需要获取所有先前日期的滚动总和，如下所示：

+------------+--------+
|    Date    | Amount |
+------------+--------+
| 01/05/2019 | NaN    |
| 27/05/2019 | 15     |
| 27/05/2019 | 15     |
| 15/06/2019 | 35     |
| 29/06/2019 | 10     |
| 01/07/2019 | 35     |
+------------+--------+

使用：

df = pd.DataFrame(
    {
        'Date': {
            0: datetime.datetime(2019, 5, 1),
            1: datetime.datetime(2019, 5, 27),
            2: datetime.datetime(2019, 5, 27),
            3: datetime.datetime(2019, 6, 15),
            4: datetime.datetime(2019, 6, 29),
            5: datetime.datetime(2019, 7, 1),
        },
        'Amount': {0: 15, 1: 20, 2: 15, 3: 10, 4: 25, 5: 50}
    }
)
df.sort_values("Date", inplace=True)
df_roll = df.rolling("28d", on="Date", closed="left").sum()

让我明白：

+------------+--------+
|    Date    | Amount |
+------------+--------+
| 01/05/2019 |    NaN |
| 27/05/2019 |     15 | 
| 27/05/2019 |     35 | <-- Should be 15
| 15/06/2019 |     35 |
| 29/06/2019 |     10 |
| 01/07/2019 |     35 |
+------------+--------+

这不太正确。

我如何获得所有先前日期而不是所有先前行的总和？

Answer 1

你可以做

df['new'] = df.Date.map(df.groupby('Date').Amount.sum().rolling("28d", closed="left").sum())
df
        Date  Amount   new
0 2019-05-01      15   NaN
1 2019-05-27      20  15.0
2 2019-05-27      15  15.0
3 2019-06-15      10  35.0
4 2019-06-29      25  10.0
5 2019-07-01      50  35.0