创建滞后数直到唯一值

Question

我有一个数据帧df，我需要有滞后值才能获得时间之间的差

df
ColA      ColB     Lag(ColB)
1      11:00:12    11:00:13
1      11:00:13    11:00:14
1      11:00:14       NA
2      11:00:15    11:00:16
2      11:00:16    11:00:17
2      11:00:17       NA
3      11:00:18    11:00:19
3      11:00:19    11:00:20
3      11:00:20       NA

仅在达到唯一值之前，我需要创建一个滞后。如果您看到，当ColA从1变为2并从2变为3时，滞后就是NA。那么有可能实现这一目标吗？

Answer 1

使用dplyr和lubridate，可以按组计算比较时间

library(dplyr)
library(lubridate)
df %>% group_by(ColA) %>% mutate(NewLag = lead(ColB)) %>%
  mutate(diff = hms(NewLag)-hms(ColB))

# A tibble: 9 x 5
# Groups:   ColA [3]
   ColA ColB     `Lag(ColB)` NewLag    diff
  <int> <chr>    <chr>       <chr>    <dbl>
1     1 11:00:12 11:00:13    11:00:13     1
2     1 11:00:13 11:00:14    11:00:14     1
3     1 11:00:14 NA          NA          NA
4     2 11:00:15 11:00:16    11:00:16     1
5     2 11:00:16 11:00:17    11:00:17     1
6     2 11:00:17 NA          NA          NA
7     3 11:00:18 11:00:19    11:00:19     1
8     3 11:00:19 11:00:20    11:00:20     1
9     3 11:00:20 NA          NA          NA