create tibble with start and end time

Question

I have an activity col and their start and end time in col time.

How can I create another tibble with three cols - activity, start_time and end_time

library(dplyr)

time <- sort(sample(x = 1:100, size = 12, replace = FALSE))
activity <- c(rep("A", 2), rep("B", 2), rep("C", 2), rep("B", 2), rep("A", 2), rep("C", 2))

tbl <- tibble(time, activity)

Answer 1

Is this what you're looking for? lead(time) computes the next value in the time variable, and slice removes one every second rows.

library(dplyr)
tbl %>% mutate(start_time = time,
               end_time = lead(time)) %>% 
  slice(seq(1, n(), by =2))

# A tibble: 6 x 4
   time activity start_time end_time
  <int> <chr>         <int>    <int>
1     3 A                 3        7
2    12 B                12       19
3    21 C                21       25
4    62 B                62       65
5    86 A                86       88
6    91 C                91       97