Create a vector with block elements of the same value

For my superfast code (no element wise evaluation of collocation points, but vector-wise) to evaluate Uniform cubic B-splines, I am looking for an answer to the following question:

I wish to create a vector that should contain this N blocks of size k the same values (starting from 1,2,3...up to N). As an example:

suppose k=3 and N=3, I want: [1 1 1 2 2 2 3 3 3 ]

I should be quite an easy thing to do, but I just can figure it out how to do it. Hope you guys can help!

[Walter Roberson]

ndgrid() or meshgrid(), take a single output and reshape it to be a vector.

I do not have access at the moment to test the exact sequence.

Answer 1

[Sean de Wolski]

K=3;
N=3;

v = reshape(repmat(1:K,N,1),1,N*K)

Answer 2

[Oleg Komarov]

Another approach, run-length decoding:

nk  = n*k;
out = zeros(1,nk);

out(1:k:nk) = 1;
out = cumsum(out);