https://github.com/cran/pracma
Tip revision: e970b8e92676e0d1f2c84b116f0bad93b03b89c6 authored by Hans W. Borchers on 15 December 2019, 21:30:02 UTC
version 2.2.9
version 2.2.9
Tip revision: e970b8e
primes.R
###
### p r i m e s . R Prime numbers
###
primes <- function(n) {
if (!is.numeric(n) || length(n) != 1)
stop("Argument 'n' must be a numeric scalar.")
n <- floor(n)
if (n < 2) return(c())
p <- seq(1, n, by=2)
q <- length(p)
p[1] <- 2
if (n >= 9) {
for (k in seq(3, sqrt(n), by=2)) {
if (p[(k+1)/2] != 0)
p[seq((k*k+1)/2, q, by=k)] <- 0
}
}
p[p > 0]
}