How to calculate combination and permutation in R?

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)
}

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

choose is also already available in the Special {base}