At the end of the inner for loop, you set
all_correct(columns,1) = correct;
Columns == 3 forever, and correct == 4 by that point. So what you are saying is
all_correct(3,1) = 4;
On the other hand, i iterates in each outer loop.
all_correct(i,1) = correct;
Note this is summing rows, not columns.
Alternatively, you could do:
x = [1 2 3 5; 4 3 1 3; 1 3 3 4];
y = [1 2 3 5; 4 3 1 3; 1 3 3 4];
correct = x==y
all_correct = sum(correct,2)
This is not only more efficient code-wise, but speed-wise (which doesn't make a difference now, but could with larger arrays). Matlab is not all that good at loops.
