Hi there, So this could very well be due to my lack of understanding of the matrix data type in opencv, so please let me know if that is the case. I have two vectors of Mat types and I am looping through all elements of all these matrices to find their respective norms as such:

```
for (k = 0; k < inp.size(); k++)
{
for (i = 0; i < inp[k].rows; i++)
{
for (j = 0; j < inp[k].cols; j++)
{
Vec2f& elem = inp[k].at<Vec2f>(i, j);
a = elem[0];
b = elem[1];
c = elem[0];
d = -elem[1];
xx+= (a*c - b*d);
elem = modelp[k].at<Vec2f>(i, j);
a = elem[0];
b = elem[1];
c = elem[0];
d = -elem[1];
yy += (a*c - b*d);
}
}
}
```

So this should be a fairly simple operations. However, after this loop the two matrices become equal! I think I am messing up the references somehow and make each pixel in one matrix to point to that of the other matrix. But I dont see how this is happening! please help me out because I am very confused. Of course the problem is fixed if I make a new reference for the calculation of the norm of the second matrix, but I still need to know why this is happening.

Thank you J