Building a matrix by merging the same row vector multiple times
You are looking for the REPMAT function:
x = [1 2 2 3];
m = repmat(x,4,1);
You can also use indexing to repeat the rows:
m = x(ones(4,1),:);
or even outer-product:
m = ones(4,1)*x;
and also using BSXFUN:
m = bsxfun(@times, x, ones(4,1))