如何从持续时间计算临时连续分组事件的开始时间和结束时间

df <- data.frame(
  grp = c("A", "B", "A", "C", "C", "A", "B", "A"),
  dur = c(111,222,33,10,555,333,600,222)
)

library(dplyr, warn.conflicts = F)
df %>%
  group_by(grp) %>%
  mutate(starttime = lag(cumsum(dur), default = 0) + 1,
    Endtime = cumsum(dur)
  )
#> # A tibble: 8 x 4
#> # Groups:   grp [3]
#>   grp     dur starttime Endtime
#>   <chr> <dbl>     <dbl>   <dbl>
#> 1 A       111         1     111
#> 2 B       222         1     222
#> 3 A        33       112     144
#> 4 C        10         1      10
#> 5 C       555        11     565
#> 6 A       333       145     477
#> 7 B       600       223     822
#> 8 A       222       478     699

或者从0开始

df %>%
  group_by(grp) %>%
  mutate(starttime = lag(cumsum(dur), default = 0),
    Endtime = cumsum(dur)
  )
#> # A tibble: 8 x 4
#> # Groups:   grp [3]
#>   grp     dur starttime Endtime
#>   <chr> <dbl>     <dbl>   <dbl>
#> 1 A       111         0     111
#> 2 B       222         0     222
#> 3 A        33       111     144
#> 4 C        10         0      10
#> 5 C       555        10     565
#> 6 A       333       144     477
#> 7 B       600       222     822
#> 8 A       222       477     699

^{于2021-07-03由 reprex package (2.0.0版)}