The LU command finds the LU decomposition of a matrix.
LU takes four arguments:
A, a numeric square matrix.
l,u and p, three variable names.
LU(A) returns the matrix P from the LU
decomposition of A, and assigns L, U and P to the variables
l,u and p. Namely, P is a permutation matrix, L is lower
triangular with ones on the diagonal, and U is upper triangular with
PA=LU.
