﻿功能:列选主元三角分解.

格式:
[P,L,U]=LUP(A)
A:一个n解方阵变量

说明:函数执行成功后返回一个名称为P的置换矩阵,然后再返回一个名称为L的下三角矩阵和一个名称为U的对角线为1的上三角矩阵.其含义即为:P*A=L*U

例子:

a =
[ 93.9290964947683    67.8490794579727    38.9889378282190    11.1702606133978
  46.0367843257435    74.5233182211049    54.3716235339509    49.0676413518692
  33.6044989217094    57.3996375116518    77.6278596732895    74.7707348665086
  34.2759118575025    29.9438441777340    17.2880263148286    59.1275361641904 ]

[p,l,u]=lup(a)//回车得到如下结果
p =
[ 1.00000000000000    0.00000000000000    0.00000000000000    0.00000000000000
  0.00000000000000    1.00000000000000    0.00000000000000    0.00000000000000
  0.00000000000000    0.00000000000000    1.00000000000000    0.00000000000000
  0.00000000000000    0.00000000000000    0.00000000000000    1.00000000000000 ]
l =
[ 93.9290964947683    0.00000000000000    0.00000000000000    0.00000000000000
  46.0367843257435    41.2689428010145    0.00000000000000    0.00000000000000
  33.6044989217094    33.1256435888910    35.3747856614996    0.00000000000000
  34.2759118575025    5.18485943392049   -1.36973332539647    50.9600987139459 ]
u =
[ 1.00000000000000    0.72234357605847    0.41508903293231    0.11892226190017
  0.00000000000000    1.00000000000000    0.85445026830195    1.05631111122550
  0.00000000000000    0.00000000000000    1.00000000000000    1.01155175320880
  0.00000000000000    0.00000000000000    0.00000000000000    1.00000000000000 ]