primefactors(n [, max:T]), n an integer scalar or vector |

primefactors(n), where n is a positive integer < 2^52 = 4503599627370496, returns a vector containing the prime factors of n, possibly with repetitions. When n is a vector of positive integers <= 999999999999 = 10^12 - 1, primefactors(n) returns a structure with length(n) components. Component i is a vector containing the prime factors of n[i] and having the numeric value of n[i] as its name. The reason for the smaller range of permissible values is because a component name can have at most 12 characters. Note: Because the component names are numeric and not alphabetic, you must use a subscript to extract a component. primefactors(n,max:T), where n is a positive integer scalar or vector with n[i] < 2^52 = 4503599627370496, returns an integer vector of the same length as n containing the maximum prime factors of each element of n. Examples: Cmd> primefactors(64094231) (1) 641 99991 Cmd> stuff <- primefactors(vector(3,15,64094231)); stuff component: 3 (1) 3 component: 15 (1) 3 5 component: 64094231 (1) 641 99991 Cmd> stuff[3] # stuff$64094231 is illegal (1) 641 99991 Cmd> stuff[compnames(stuff) == "64094231"] (1) 641 99991 Cmd> primefactors(64094231, max:T) (1) 99991 See also goodfactors().

Gary Oehlert 2003-01-15