Project Euler Problem #7 (R)

Problem 7 on the Project Euler site is the following challenge:

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.

What is the 10001st prime number?

The routine below returns a list of primes, each successive prime being calculated by testing none of the currently known primes divide the current integer counter value evenly. If not, the current integer value is added to the list of known primes.

nprime <- function(n) {
        if (n == 1) {
                return (2)
        }
        psofar <- c()
        psofar[1] <- 2
        j <- 2
        p <- 1
        i <- 2
        while (p < n)  {
                if ( all((i %% psofar) > 0) ) {
                        psofar[j] <- i
                        j <- j + 1
                        p <- p + 1
                }
                i <- i + 1
        }
        psofar
}

To return the 10001^st prime, we invoke it like so:

>tail(psofar(10001),1)