R help - Jul 2007 - create an array with rep

Hi,


I want to make the following array of numbers:

-3 -3 -3 -3 -3 -3 -3 -2 -2 -2 -2 -2 -2 -2 ...  3  3  3  3  3  3  3
-3 -2 -1  0  1  2  3 -3 -2 -1  0  1  2  3 ... -3 -2 -1  0  1  2  3

(3 would be N, a painful example to type number).

Here is my dirty attempt to do it,
> N<-3
>
> x<-c(-N:N)
>
> rj<-rbind(matrix(outer(matrix(1,1,2*N+1),x),nrow=1),rep(x,2*N+1))
>
It sort of works, but I'd like some advice on how to do it properly  
as I'm very new to R and N may be big at some point.

Thanks,

baptiste

try this:

x <- -3:3
as.matrix(expand.grid(x, x))
# or
t(as.matrix(expand.grid(x, x)))


I hope it helps.

Best,
Dimitris


----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
      http://www.student.kuleuven.be/~m0390867/dimitris.htm


Quoting baptiste Augui? <ba208 at exeter.ac.uk>:
>
> Hi,
>
>
> I want to make the following array of numbers:
>
> -3 -3 -3 -3 -3 -3 -3 -2 -2 -2 -2 -2 -2 -2 ...  3  3  3  3  3  3  3
> -3 -2 -1  0  1  2  3 -3 -2 -1  0  1  2  3 ... -3 -2 -1  0  1  2  3
>
> (3 would be N, a painful example to type number).
>
> Here is my dirty attempt to do it,
>
>> N<-3
>>
>> x<-c(-N:N)
>>
>> rj<-rbind(matrix(outer(matrix(1,1,2*N+1),x),nrow=1),rep(x,2*N+1))
>>
>
> It sort of works, but I'd like some advice on how to do it properly
> as I'm very new to R and N may be big at some point.
>
> Thanks,
>
> baptiste
>
> ______________________________________________
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>
>


Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm

On 7/22/07, Dimitris Rizopoulos <Dimitris.Rizopoulos at med.kuleuven.be>
wrote:
> try this:
>
> x <- -3:3
> as.matrix(expand.grid(x, x))
> # or
> t(as.matrix(expand.grid(x, x)))
One minor shortening:

t(expand.grid(x, x))

Thank you all!

This looks like the fastest solution, N being big and my machine slow  
I'll go for this one.

Thanks,

baptiste

On 22 Jul 2007, at 12:54, Gavin Simpson wrote:
>>
>> I want to make the following array of numbers:
>>
>> -3 -3 -3 -3 -3 -3 -3 -2 -2 -2 -2 -2 -2 -2 ...  3  3  3  3  3  3  3
>> -3 -2 -1  0  1  2  3 -3 -2 -1  0  1  2  3 ... -3 -2 -1  0  1  2  3
>>
>> (3 would be N, a painful example to type number).
>
> This does what you want:
>
> foo <- function(N) {
>    reps <- 2*N+1
>    matrix(c(rep(-N:N, each = reps), rep(-N:N, times = reps)),
>           nrow = 2, byrow = TRUE)
> }