Tiling Matrix row by row

Question

I want to repeat each row n times, for example:

A= [123
    456
    789];

so I want to have:

b=[123
   123
   123
   456
   456
   456
   789
   789
   789];

I have tried repmat:

B = repmat(A,3,1)

But this does not result in the b above...How do I do this?

Answer 1

Rody has provided you with the repmat solution (+1), but I thought it was also worth pointing out that:

A = [123;456;789];
A = ones(N, 1) * A';
A = A(:);

will be close to an order of magnitude faster, since repmat isn't a particularly efficient function. A quick speed test over 10000 iterations yields:

Elapsed time is 0.206894 seconds %#repmat solution
Elapsed time is 0.024718 seconds %#My solution

A final point, I notice in the comments that @Maroun85 suggests using linear indexing. However, I can't see a clever way to construct the required index without a call to repmat, which brings us back to the original source of slow-down. Someone else might be able to come up with a clever way to construct the required index vector though.

EDIT: Rody has updated his answer to provide the aforementioned "clever way". :-)