Revision 04bbc417cf2927b827660bc07743429783569aec authored by HwB on 10 February 2013, 00:00:00 UTC, committed by Gabor Csardi on 10 February 2013, 00:00:00 UTC
1 parent 0e3ae6b
factors.R
###
### f a c t o r s . R Factorize natural number
###
factors <- function(n) {
if (!is.numeric(n) || length(n) != 1 || n != round(n) || n < 1)
stop("Argument 'n' must be a nonnegative integer.")
if (n >= 2^53)
stop("Argument 'n' must not be larger than 2^53-1.")
if (n < 4) return(n)
f <- c()
p <- primes(sqrt(n))
d <- which(n %% p == 0)
if (length(d) == 0) return(n) # n is prime
for (q in p[d]) {
while (n %% q == 0) {
f <- c(f, q)
n <- n/q
}
}
if (n > 1) f <- c(f, n)
return(f)
}
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