[L1,U1]=lu(x)
[L2,U2,P]=lu(x)
[L3,U3,P,Q] = lu(X)
MATLAB中[L1,U1]=lu(x)的结果:L是下三 角的置换矩阵即L1=p*L2,U是上三角阵。Matlab中LU分解采用高斯消元法,结果是不唯一的,只要[L1,U1]=lu(x)满足 L1*U1=x, [L2,U2,P]=lu(x)满足L2*U2=p*x,[L3,U3,P,Q] = lu(X)满足 L3*U3= P*X*Q就行了
http://www.ilovematlab.cn/thread-71643-1-1.html