zephyr21 - when I run your code, my b is a 1x108 matrix. How do you get a 217x1 and why do you think that the result should be a 122x1? Since your i iterates from 2 through 10 and j iterates from 2 through 13, then b should be 9*12=108 elements.
In your code, I would remove the inner-most for loop and just replace this with
for j=2:13
m = m + 1;
b(m) = Q(i,j);
end
Also, try to avoid using i and j as the names of indexing variables (for your loops) since MATLAB uses both to represent the imaginary number.
And...you may want to look at reshape which can be used (for example) to reshape your matrix into a column vector.
