[R] Error in rep.int() invalid 'times' value
PIKAL Petr
petr.pikal at precheza.cz
Tue Oct 20 15:27:52 CEST 2015
Hi
Why are you confused?
> f0(5,3)
[,1] [,2]
[1,] 0 0
[2,] 1 0
[3,] 2 0
[4,] 0 1
[5,] 1 1
[6,] 0 2
> f1(5,3)
[,1] [,2]
[1,] 0 0
[2,] 1 0
[3,] 2 0
[4,] 0 1
[5,] 1 1
[6,] 0 2
>
seems to give the same result.
> res0<-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
> res1<-f1(25,15)
So f1 works for required m,n.
William just used different approach to get the same result, which is indeed quite common in R.
Cheers
Petr
From: Maram SAlem [mailto:marammagdysalem at gmail.com]
Sent: Tuesday, October 20, 2015 1:50 PM
To: PIKAL Petr
Cc: r-help at r-project.org
Subject: Re: [R] Error in rep.int() invalid 'times' value
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<mailto: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<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<mailto:r-help at r-project.org>
> Subject: Re: [R] Error in rep.int<http://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<http://rep.int>(rep.int<http://rep.int>(seq_len(nx), rep.int<http://rep.int>(rep.fac, nx)), orep) :
> invalid 'times' value
> In addition: Warning message:
> In rep.int<http://rep.int>(rep.int<http://rep.int>(seq_len(nx), rep.int<http://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<mailto: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<http://tibco.com>
> >
> > On Thu, Oct 15, 2015 at 7:45 AM, Maram SAlem
> > <marammagdysalem at gmail.com<mailto: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<http://rep.int>(rep.int<http://rep.int>(seq_len(nx), rep.int<http://rep.int>(rep.fac, nx)), orep) :
> >> invalid 'times' value
> >> In addition: Warning message:
> >> In rep.int<http://rep.int>(rep.int<http://rep.int>(seq_len(nx), rep.int<http://rep.int>(rep.fac, nx)), orep) :
> >> NAs introduced by coercion to integer range
> >>
> >>
> >> Any help or suggestions will be greatly appreciated.
> >>
> >> Thanks,
> >>
> >> Maram Salem
> >>
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