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

[Maram SAlem]

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]]
>>
>> ______________________________________________
>> R-help at 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]]