[r] How to calculate combination and permutation in R?

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)

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

choose is also already available in the Special {base}

It might be that the package "Combinations" is not updated anymore and does not work with a recent version of R (I was also unable to install it on R 2.13.1 on windows). The package "combinat" installs without problem for me and might be a solution for you depending on what exactly you're trying to do.

The Combinations package is not part of the standard CRAN set of packages, but is rather part of a different repository, omegahat. To install it you need to use

install.packages("Combinations", repos = "http://www.omegahat.org/R")

See the documentation at http://www.omegahat.org/Combinations/

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)
}