Thanks. That's what I want. Sorry for the typo:)

Feng

On Mon, Sep 13, 2010 at 11:42 AM, Ted Harding
<Ted.Harding@manchester.ac.uk>wrote:

> On 13-Sep-10 09:19:21, Feng Li wrote:
> > Dear R,
> > I have a vector, say a = c(1,2,4,5,6,8). Can I generate a vector
> > or array (2-by-3-by-3) of this form
> > c(1,2,1,2,1,2,4,5,4,5,4,5,6,8,6,8,6,8)
> > in which every two elements in "a" have been repeated twice?
> >
> > I am to stupid today and could not figure this simple question out...
> > Many many thanks!
> >
> > Feng
>
> A possible solution (somewhat generalisable):
>
>  a <- c(1,2,4,5,6,8)
>   Reps <- 3
>
>  pairs <- matrix(a,nrow=2)
>  as.vector(pairs[,rep(c(1,2,3),each=Reps)])
>  # [1] 1 2 1 2 1 2 4 5 4 5 4 5 6 8 6 8 6 8
>
> (By the way, you have 3 repetitions but wrote "twice" -- I assume
> you meant "thrice" but the above generalises to 2 repetitions ... :)
>
> Ted.
>
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> E-Mail: (Ted Harding) <Ted.Harding@manchester.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 13-Sep-10                                       Time: 10:42:46
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>



-- 
Feng Li
Department of Statistics
Stockholm University
106 91 Stockholm, Sweden
http://feng.li/

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