[R] (Most efficient) way to make random sequences of random sequences

[Rolf Turner]

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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