How can I break a row to multiple rows based on interval

Question

My data looks like this:

das <- data.frame(val=1:3,
                  beginning =c(10,20,40),
                  end=c(20,40,51))

  val beginning end
1   1        10  20
2   2        20  40
3   3        40  51

I want to break each row to 3 rows by dividing the beginning to end to equal parts. like this

Expected output

> das
  val beginning end
1   1        10  13
2   2        13  16
3   3        16  20
4   4        20  27
5   5        27  34
6   6        34  40
7   7        40  44
8   8        44  48
9   9        48  51

I came across similar questions here, but most of them are w.r.t to date range.

Answer 1

You can use uncount() in tidyr and then calculate the increment of each val.

library(dplyr)
library(tidyr)

das %>%
  uncount(3) %>% 
  mutate(beginning = beginning + round((end - beginning)/3) * 0:2,
         end = lead(beginning, default = last(end)))

#   val beginning end
# 1   1        10  13
# 2   1        13  16
# 3   1        16  20
# 4   2        20  27
# 5   2        27  34
# 6   2        34  40
# 7   3        40  44
# 8   3        44  48
# 9   3        48  51