Is there an R function to get the number of permutations of n objects take k P(n,k)?

Question

..or do I have to give ``` P.nk <- factorial(n) / factorial(n-k) ``` or ``` P.nk <- choose(n,k) * factorial(k) ``` Thank you.

Accepted Answer

I don't know of any existing function. Your first suggestion will fail with large n. Your second idea should work fine when written as a function:

```
perm <- function(n,k){choose(n,k) * factorial(k)}
```

Then `perm(500,2)` will give 249500 for example.

Solution