R/permutations.R

In ropensci/DoOR.functions: Integrating Heterogeneous Odorant Response Data into a Common Response Model: A DoOR to the Complete Olfactome

# calculate all possible permutations
#
# @param n length of vector to permute
#
# code from http://stackoverflow.com/questions/11095992/generating-all-distinct-
# permutations-of-a-list-in-r
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)
  }
}