Hi LK
There is nothing really wrong here. 'help lu' tells you that [L U] = lu(A) gives a row-permuted L matrix (it's not necessarily lower triangular any more) so that A = LU. The command [L U P] = lu(A) gives a true lower triangular matrix L and a permutation matrix P such that PA = LU, or (since P' is the inverse of P), A = P'LU. All of this done to allow pivoting so that the computed L and U have maximal numerical accuracy.
