inst/notes.md

In randy3k/arrangements: Fast Generators and Iterators for Permutations, Combinations, Integer Partitions and Compositions

Some notes for future me.

stirling2 <- function(n, k) {
    partitions(n, k, layout = "l") %>% 
      map_dbl(~ npermutations(freq = .) / prod(factorial(table(.[. > 0])))) %>%
      sum
}

bell <- function(n) {
    partitions(n, layout = "l") %>% 
      map_dbl(~ npermutations(freq = .) / prod(factorial(table(.[. > 0])))) %>%
      sum
}

ordered_bell <- function(n) {
    compositions(n, layout = "l") %>% 
        map_dbl(~ npermutations(freq = .)) %>% 
        sum
}

randy3k/arrangements documentation built on May 3, 2023, 8:36 p.m.