factor {cwhmisc} | R Documentation |
Create primes, determine the prime factors of an integer (first row) together with their multiplicities (second row), recombine factors, primitive version of the sieve of Eratosthenes.
primes( n) Eratosthenes( n ) factorN( n ) allFactors( n ) prodN( fp ) is.prime( n )
n |
positive integer, number of primes, number to be factored, to be tested |
fp |
2-colummn matrix with prime factors and multiplicities |
primes |
Generate the first n primes, also found in PRIMES. |
Eratosthenes |
Execute the sieve of Eratosthenes. |
factorN |
Determine the prime factors together with their multiplicities. |
allFactors |
generate all factors of n: 1..n. |
prodN |
Recombine factors, inverse of factorN. |
is.prime |
Check if positive integer is prime. |
PRIMES |
The first primes up to 17389. |
Christian W. Hoffmann <hristian@echoffmann.ch>
(p <- factorN( 423)) ## [1,] 3 47 ## [2,] 2 1 # meaning 423 = 3^2 * 47^1 prodN(p) # 423 is.prime(.Machine$integer.max) # TRUE is.prime(16) # FALSE ## check speed of your machine s <- Sys.time(); p<-primes(10^4);difftime(Sys.time(),s) ## Time difference of 1.578922 secs on my machine x <- factorN(.Machine$integer.max)