How to calculate combination and permutation in R?

Question

How one can calculate the number of combinations and permutations in R?

The Combinations package failed to install on Linux with the following message:

> install.packages("Combinations") Installing package(s) into ‘/home/maxim/R/x86_64-pc-linux-gnu-library/2.13’ (as ‘lib’ is unspecified) Warning message: In getDependencies(pkgs, dependencies, available, lib) :   package ‘Combinations’ is not available (for R version 2.13.1) 

Answer 1

The function combn is in the standard utils package (i.e. already installed)

choose is also already available in the Special {base}

Answer 2

If you don't want your code to depend on other packages, you can always just write these functions:

perm = function(n, x) {   factorial(n) / factorial(n-x) }  comb = function(n, x) {   factorial(n) / factorial(n-x) / factorial(x) }