第四题LU函数

lu_decompose.m

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+function [L,U] = lu_decompose(A)
+%   lu decompose
+%   L:下三角矩阵
+%	U:上三角矩阵
+%	A:输入矩阵
+[m,n]=size(A);
+
+L=eye(m);
+L(:,1)=A(:,1)/A(1,1);%L第一列赋值
+
+U=zeros(m,n);
+U(1,:)=A(1,:);%U第一行赋值
+
+for i=2:m
+    for j=2:n
+        if i<=j
+            U(i,j)=A(i,j)-sum(L(i,1:i-1).*U(1:i-1,j)');%递推表达式(1-6)
+        else
+            if U(j,j)==0
+                L(i,j)=0;
+            else
+                L(i,j)=(A(i,j)-sum(L(i,1:j-1).*U(1:j-1,j)'))/U(j,j);%递推表达式(1-7)
+            end
+        end
+    end
+end
+
+
+
+
+
+