Sorry - I didn't express myself very clearly. Yes, we're looking for common factors of A and B. One way to get there is by my initial approach: find the prime factors of each, select those that are in common, and then take pairwise products. My initial question was about the last step only. But your approach to the whole problem sidesteps that. It's more elegant, as well as faster, than the way I thought of the problem.
Gordon Stavros Macrakis wrote: > On Wed, Feb 25, 2009 at 9:25 AM, Fox, Gordon <g...@cas.usf.edu> wrote: > >> The tricky part isn't finding the common factors -- we knew how to do >> that, though not in so concise a fashion as some of these suggestions. >> It was finding all their products without what I (as a recovered Fortran >> programmer) would call "truly brute force." Several of these suggestions >> solve the problem nicely! >> > > Are you sure you are not confusing *prime factors* with *factors*? My > understanding is that you are looking for all the factors of A which > are also factors of B, i.e. the common factors of A and B. Why else > would you be computing all those products? > > -s > -- Dr. Gordon A. Fox Voice: (813)974-7352 Fax: (813)974-3263 Dept. of Integrative Biology ((for US mail:)SCA 110) ((for FedEx etc:)NES 107) Univ. of South Florida 4202 E. Fowler Ave. Tampa, FL 33620, USA http://foxlab.cas.usf.edu "Trying is the first step towards failure." -- Homer Simpson [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
