R/permutations.R

In UNCLES: Unification of Clustering Results from Multiple Datasets using External Specifications

permutations <- function(n) {
    if (n == 1) {
        return(matrix(1))
    } else {
        sp <- permutations(n - 1)
        p <- nrow(sp)
        A <- matrix(nrow = n * p, ncol = n)
        for (i in 1:n) {
            A[(i - 1) * p + 1:p,] <- cbind(i, sp + (sp >= i))
        }
        return(A)
    }
}