R/perms.R

In ANSM5: Functions and Data for the Book "Applied Nonparametric Statistical Methods", 5th Edition

#' Creates matrix of permutations
#'
#' @description
#' `perms()` creates a matrix containing all permutations of an integer number of items
#'
#' @param n Integer
#' @returns A matrix
#'
#' @keywords internal
#' @noRd
perms <-
  function(n){
    if(n == 1){
      return(matrix(1))
    }else{
      prev <- perms(n - 1)
      p <- nrow(prev)
      perms_out <- matrix(nrow = n * p, ncol = n)
      for(i in 1:n){
        perms_out[(i - 1) * p + 1:p,] <- cbind(i , prev + (prev >= i))
      }
      return(perms_out)
    }
  }