Thanks for the hint Petr. I'm just a little bit confused with the function f1(). could you please help me and insert comments within f1() to be able to relate it with f0()?
Thanks a lot. Maram Salem On 20 October 2015 at 11:29, PIKAL Petr <petr.pi...@precheza.cz> wrote: > Hi > > What about using the second function f1 which William suggested? > > Cheers > Petr > > > > -----Original Message----- > > From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Maram > > SAlem > > Sent: Tuesday, October 20, 2015 11:06 AM > > To: William Dunlap; r-help@r-project.org > > Subject: Re: [R] Error in rep.int() invalid 'times' value > > > > Thanks William. I've tried the first code, ( with f0() ), but still for > > n=25, m=15 , I got this: > > > > > s<-f0(25,15) > > Error in rep.int(rep.int(seq_len(nx), rep.int(rep.fac, nx)), orep) : > > invalid 'times' value > > In addition: Warning message: > > In rep.int(rep.int(seq_len(nx), rep.int(rep.fac, nx)), orep) : > > NAs introduced by coercion to integer range > > > > > > I don't know if this is related to the memory limits of my laptop, or > > it doesn't have to do with the memory. > > > > Any help on how to fix this error will be greatly appreciated. > > > > Thanks All. > > > > Maram Salem > > > > On 15 October 2015 at 17:52, William Dunlap <wdun...@tibco.com> wrote: > > > > > Doing enumerative combinatorics with rejection methods rarely works > > > well. Try mapping your problem to the problem of choosing > > > m-1 items from n-1. E.g., your code was > > > > > > f0 <- function(n, m) { > > > stopifnot(n > m) > > > D<-matrix(0,nrow=n-m+1,ncol=m-1) > > > for (i in 1:m-1){ > > > D[,i]<-seq(0,n-m,1) > > > } > > > ED <- do.call(`expand.grid`,as.data.frame(D)) > > > ED<-unname(as.matrix(ED)) > > > lk<-which(rowSums(ED)<=(n-m)) > > > ED[lk,] > > > } > > > > > > and I think the following does the same thing in much less space by > > > transforming the output of combn(). > > > > > > f1 <- function(n, m) { > > > stopifnot(n > m) > > > r0 <- t(diff(combn(n-1, m-1)) - 1L) > > > r1 <- rep(seq(from=0, len=n-m+1), choose( seq(to=m-2, by=-1, > > > len=n-m+1), m-2)) > > > cbind(r0[, ncol(r0):1, drop=FALSE], r1, deparse.level=0) } > > > > > > The code for adding the last column is a bit clumsy and could > > probably > > > be improved. Both f0 and f1 could also be cleaned up to work for > > m<=2. > > > > > > See Feller vol. 1 or Benjamin's "Proofs that (really) count" for more > > > on this sort of thing. > > > > > > > > > > > > Bill Dunlap > > > TIBCO Software > > > wdunlap tibco.com > > > > > > On Thu, Oct 15, 2015 at 7:45 AM, Maram SAlem > > > <marammagdysa...@gmail.com> > > > wrote: > > > > > >> Dear All, > > >> > > >> I'm trying to do a simple task (which is in fact a tiny part of a > > >> larger code). > > >> > > >> I want to create a matrix, D, each of its columns is a sequence from > > >> 0 to (n-m), by 1. Then, using D, I want to create another matrix ED, > > >> whose rows represent all the possible combinations of the elements > > of > > >> the columns of D. Then from ED, I'll select only the rows whose sum > > >> is less than or equal to (n-m), which will be called the matrix s. I > > used the following code: > > >> > > >> > n=5 > > >> > m=3 > > >> > D<-matrix(0,nrow=n-m+1,ncol=m-1) > > >> > for (i in 1:m-1) > > >> + { > > >> + D[,i]<-seq(0,n-m,1) > > >> + } > > >> > ED <- do.call(`expand.grid`,as.data.frame(D)) > > >> > ED<-as.matrix(ED) > > >> > > >> > lk<-which(rowSums(ED)<=(n-m)) > > >> > > >> > s<-ED[lk,] > > >> > > >> > > >> This works perfectly well. But for rather larger values of n and m > > >> (which are not so large actually), the number of all possible > > >> combinations of the columns of D gets extremely large giving me this > > error (for n=25, m=15): > > >> > > >> > ED <- do.call(`expand.grid`,as.data.frame(D)) > > >> Error in rep.int(rep.int(seq_len(nx), rep.int(rep.fac, nx)), orep) : > > >> invalid 'times' value > > >> In addition: Warning message: > > >> In rep.int(rep.int(seq_len(nx), rep.int(rep.fac, nx)), orep) : > > >> NAs introduced by coercion to integer range > > >> > > >> > > >> Any help or suggestions will be greatly appreciated. > > >> > > >> Thanks, > > >> > > >> Maram Salem > > >> > > >> [[alternative HTML version deleted]] > > >> > > >> ______________________________________________ > > >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > > >> 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 -- To UNSUBSCRIBE and more, see > > 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. > > ________________________________ > Tento e-mail a jakékoliv k němu připojené dokumenty jsou důvěrné a jsou > určeny pouze jeho adresátům. > Jestliže jste obdržel(a) tento e-mail omylem, informujte laskavě > neprodleně jeho odesílatele. 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