[Solved] is there a R code for group_by and combinations

by


I am not sure if the code below is what you are after

out1 <- ds %>%
    group_by(id) %>%
    summarise(n = n()) %>%
    mutate(ncomb2 = choose(n,2))

such that

> out1
# A tibble: 3 x 3
     id     n ncomb2
  <dbl> <int>  <dbl>
1     1     4      6
2     2     4      6
3     3     4      6

solved is there a R code for group_by and combinations