factorN: Create primes, factor an integer, combine factors, check if...

In cwhmisc: Miscellaneous Functions for Math, Plotting, Printing, Statistics, Strings, and Tools

Description

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.

Usage

primes( n)
Eratosthenes( n )
factorN( n )
allFactors( n )
prodN( fp )
is.prime( n )

Arguments

n	positive integer, number of primes, number to be factored, to be tested
fp	2-colummn matrix with prime factors and multiplicities

Value

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.

Author(s)

Christian W. Hoffmann <[e-mail]>

Examples

(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)

cwhmisc documentation built on May 1, 2019, 7:55 p.m.