R help - Aug 2007 - (Most efficient) way to make random sequences of random sequences

Hi,

I was wondering the what would be the (most efficient) way to generate
a sequence
of sequences, i mean:

if I have 1,2 and 3.

I'd like to generate a sequence of length N*3 (N ~ 1,000,000 or more)

Where random permutations of the sequence 1,2,3 follow each other.

i.e  1,2,3,1,3,2,3,2,1

/!\ The thing is that there should never be twice the same number of
in the same sub-sequence, meaning that this is different from
generating a vector with the numbers 1,2 and 3 randomly distributed.

Any suggestion very welcome! Thanks,

Emmanuel

One way:

	N <- 10
	 s <- c(apply(matrix(rep(1:3,N),3,N),2,sample))


url:    www.econ.uiuc.edu/~roger            Roger Koenker
email    rkoenker at uiuc.edu            Department of Economics
vox:     217-333-4558                University of Illinois
fax:       217-244-6678                Champaign, IL 61820


On Aug 21, 2007, at 3:49 PM, Emmanuel Levy wrote:
> Hi,
>
> I was wondering the what would be the (most efficient) way to generate
> a sequence
> of sequences, i mean:
>
> if I have 1,2 and 3.
>
> I'd like to generate a sequence of length N*3 (N ~ 1,000,000 or more)
>
> Where random permutations of the sequence 1,2,3 follow each other.
>
> i.e  1,2,3,1,3,2,3,2,1
>
> /!\ The thing is that there should never be twice the same number of
> in the same sub-sequence, meaning that this is different from
> generating a vector with the numbers 1,2 and 3 randomly distributed.
>
> Any suggestion very welcome! Thanks,
>
> Emmanuel
>
> ______________________________________________
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> guide.html
> and provide commented, minimal, self-contained, reproducible code.

On 22/08/2007, at 8:49 AM, Emmanuel Levy wrote:
> Hi,
>
> I was wondering the what would be the (most efficient) way to generate
> a sequence
> of sequences, i mean:
>
> if I have 1,2 and 3.
>
> I'd like to generate a sequence of length N*3 (N ~ 1,000,000 or more)
>
> Where random permutations of the sequence 1,2,3 follow each other.
>
> i.e  1,2,3,1,3,2,3,2,1
>
> /!\ The thing is that there should never be twice the same number of
> in the same sub-sequence, meaning that this is different from
> generating a vector with the numbers 1,2 and 3 randomly distributed.
	require(gtools)
	m <- permutations(3,3)
	M <- m[sample(1:6,1000000,TRUE),]
	x   <- as.vector(t(M))

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