help lu
% LU Factors from Gaussian elimination.
% [L,U] = LU(X) stores a upper triangular matrix in U and a
% "psychologically lower triangular matrix", i.e. a product
% of lower triangular and permutation matrices, in L , so
% that X = L*U.
%
% [L,U,P] = LU(X) returns lower triangular matrix L, upper
% triangular matrix U, and permutation matrix P so that
% P*X = L*U.
%
% By itself, LU(X) returns the output from LINPACK'S ZGEFA
% routine
[l,u,p] = lu(A)