[R] Error in rep.int() invalid 'times' value

[Maram SAlem]

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.pikal at precheza.cz> wrote:

> Hi
>
> What about using the second function f1 which William suggested?
>
> Cheers
> Petr
>
>
> > -----Original Message-----
> > From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Maram
> > SAlem
> > Sent: Tuesday, October 20, 2015 11:06 AM
> > To: William Dunlap; r-help at 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 <wdunlap at 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
> > > <marammagdysalem at 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]]
> > >>
> > >> ______________________________________________
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> > >>
> > >
> > >
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
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