MATLAB: Create consecutive duplicates of rows

Question

I have a vector A, for example (1:1:5)' I want to create a new vector B in which each row from vector A is repeated, for example 5 times. So A is [1 2 3 4 5]' and B is [1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5]'

I have been able to accomplish this with the for loop below, but this takes much too long as my real vector A is over 2 million rows long. Is there a more computationally efficient way to accomplish this?

numbreps=5; for k=1:size(A); B(k*numbreps:k*numbreps+numbreps-1,1)=A(k,1); end; B(1:numbreps-1)=[];

Answer 1

a=(1:5)'
b=repmat(a',5,1)
b=b(:)