Dear Gordon, Try also, > unique(apply(expand.grid(commfac,commfac),1,prod)) [1] 1 2 5 4 10 25
HTH, Jorge On Mon, Feb 23, 2009 at 9:52 PM, Fox, Gordon <g...@cas.usf.edu> wrote: > This is a seemingly simple problem - hopefully someone can help. > Problem: we have two integers. We want (1) all the common factors, and > (2) all the possible products of these factors. We know how to get (1), > but can't figure out a general way to get (2). > > > > Example: 40 and 80 have these factors: c(1,2,2,2,5) and c(1,2,2,2,2,5). > We can use match() to get the common factors c(1,2,2,2,5). What we want > to be able to get from this is the list of all the possible products, > which should be the concatenation of the original list, the products of > all the pairs, of all the triplets, and so forth: > c(1,2,2,2,5,4,8,10,20,40). > > > > The application is this: we have an area that is, say, 40 x 80 units. We > want to find all the possible grids (of square integer-valued units) > that can be placed over that area that cover it completely. The list at > the end of the preceding paragraph is the right answer - the question is > how to get it from our list of common factors, other than by brute > force. > > > > Thanks for any advice. > > > > Gordon > > > > -- > > 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 > > "All the fun of sitting still, being quiet, writing down numbers. Yes, > science has it all." -- Principal Skinner > > > > > [[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. > [[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.
