Question

求矩阵LU分解的matlab代码

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Answer 1

function[L U flag]= LU_Decom(A)
[n,m]=size(A);
if n~=m
error('The rows and the columns of the matrix A must be equal!')
return;
end
flag='OK'; L=eye(n);U=zeros(n);
for k=1:n
for j=k:n
z=0;
for q=1:k-1
z=z+L(k,q)*U(q,j);
end
U(k,j)=A(k,j)-z;
end
if abs(U(k,k))< eps
flag='failure';return;
end
for i=k+1:n
z=0;
for q=1:k-1
z=z+L(i,q)*U(q,k);
end
L(i,k)=(A(i,k)-z)/U(k,k);
end
end

Answer 2

不选主元的
function [L,U] = mylu(A)
[n,n]=size(A);
L=eye(n);
U=A;
for i=1:n-1
if A(i,i) == 0
fprintf('Error: A(%d,%d)=0!\n', i,i); return;
end
for j=i+1:n
L(j,i)=A(j,i)/A(i,i);
end
for k=i+1:n
for l=i:n
A(k,l)=A(k,l)-L(k,i)*A(i,l);
end
end
end
U=A;