Calculates the total number of ways to arrange k items selected from n distinct items, i.e.,
the number of permutations A(n, k) = n! / (n - k)!.
This function is intended for moderate n and k. For very large numbers, consider supporting the 'gmp' package.
Arguments
- n
Integer. Total number of items (non-negative integer).
- k
Integer. Number of items selected for permutation (non-negative integer, must be <= n).
Value
Numeric. The permutation count A(n, k) (returns Inf for very large n).
Examples
perm(8, 4) # 1680
#> [1] 1680
perm(5, 2) # 20
#> [1] 20
perm(10, 0) # 1
#> [1] 1
perm(5, 6) # 0
#> [1] 0
