R/perm.n.k.R

In dco61/isteahMAT104: MAT104 Probabilité et Statistiques

#'
#'
#' Compute number of Permutations of n objects taken k at a time
#'
#' @param n Number of items to permute (numeric/alphanumeric)
#' @param k Number of items selected from set
#' @return Number of permutations of n objects taken k at a time
#' @examples
#' p1 <- perm.n.k(n=6,k=2)
#' p2 <- perm.n.k(10,4)
#' @export
perm.n.k <- function(n, k) {
    if (!testInt(n)) {
        stop("n must be an integer value!")
    }
    if (!testInt(k)) {
        stop("k must be an integer value!")
    }
    if (k > n) {
        stop("n must be greater or equal to k!")
    }
    prm <- factorial(n)/factorial(n - k)
    return(prm)
}