Help creating Doolittle LU factorization.

Good day!

I'm trying to create my own Doolittle's

However I'm encountering an error from the while statement.

What I'm trying to do is, when element (P,R) in the L is equal to zero, it will try get replaced by the below equation,the column value will be added by one until the element is not equal to 0 (equal to 1 of the diagonal).

I'm not sure either if my equation is correct either. Since I'm very new to Matlab itself. When I try to display L, the zeroes starting from L(3,2) did not get replaced.

Thank you

Edit: I manged to deal with the previous problem. But still, L(P,R) does not get replaced in the row after