Find All Primes Less Than n
Find all prime numbers aka ‘primes’ less than n.
Uses an obvious sieve method and some care, working with logical and integers to be quite fast.
Primes(n)
n |
a (typically positive integer) number. |
As the function only uses max(n), n can also be a
vector of numbers.
numeric vector of all prime numbers <= n.
This function was previously published in the package sfsmisc as primes
and has been integrated here without logical changes.
Bill Venables (<= 2001); Martin Maechler gained another 40% speed, working with logicals and integers.
(p1 <- Primes(100)) system.time(p1k <- Primes(1000)) # still lightning .. stopifnot(length(p1k) == 168)
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