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]]
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]]
marammagdysalem at gmail.com
2015-Oct-16 09:17 UTC
[R] Error in rep.int() invalid 'times' value
Thanks a lot for helping William. Will check the reference as well. Sent from my iPhone> On Oct 15, 2015, at 5:52 PM, 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]]
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]]