有下面这个表格,id=1和id=2各有5组数据
| Obs | ID | Repetition | species | Treatment | Week | Activity | censor | lower | upper |
| 1 | 1 | a | alba | 1 | 14 | 0 | 0 | 14 | 14 |
| 2 | 1 | a | alba | 1 | 21 | 2 | 0 | 21 | 21 |
| 3 | 1 | a | alba | 1 | 28 | 3 | 0 | 28 | 28 |
| 4 | 1 | a | alba | 1 | 35 | . | 1 | . | . |
| 5 | 1 | a | alba | 1 | 42 | . | 1 | . | . |
| 6 | 2 | b | alba | 1 | 14 | 0 | 0 | 14 | 14 |
| 7 | 2 | b | alba | 1 | 21 | 2 | 0 | 21 | 21 |
| 8 | 2 | b | alba | 1 | 28 | 3 | 0 | 28 | 28 |
| 9 | 2 | b | alba | 1 | 35 | . | 1 | . | . |
| 10 | 2 | b | alba | 1 | 42 | . | 1 | . | . |
想要得到下面这样的数据,也就是当id=1时,activity第一次为.时,它的lower为上一行的week,它的upper为现在这一行的week
同理id=2。(因为是在week=35时,activity为. , 所以下面的结果里lower为28(上一周week是28),upper为35(这一周week是35)
| Obs | ID | Repetition | species | Treatment | Week | Activity | censor | lower | upper |
| 4 | 1 | a | alba | 1 | 35 | . | 1 | 28 | 35 |
| 9 | 2 | b | alba | 1 | 35 | . | 1 | 28 | 35 |