for loops in MATLAB loop over the columns of the variable you tell it. So, for example, this:
for i = [1 2 3]
display(i);
end
is as expected (columns of a row vector are scalars), but the following only loops once and i is the whole column vector:
for i = [1; 2; 3]
display(i);
end
Generalizing to a 2d matrix:
x = magic(3);
for i = x
display(i);
end
So in your second example (without transposing y), n takes the value [3; 4] and the loop iterates once, rather than the loop iterating twice with n taking 3 and then 4, which is what it does in the first example.
