the loop is not converging it is giving me an infinite value(it is increasing)

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Mahmoud Chawki 2023-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/1968779-the-loop-is-not-converging-it-is-giving-me-an-infinite-value-it-is-increasing

移动：Matt J 2023-5-20

clear variables
close all
clc
A = [1 1 2; 1 2 4; 1 2 5];
x = [1; 2; 3];
Error = 0.00001;
Diff= 1;
while Diff>Error
    
    x1=A*x;
    
    
    Diff=norm(x1-x);
    
    x=x1;
end

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Mahmoud Chawki 2023-5-20

still not working still not working the answer is infinity for x and NAN for Diff

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回答（1 个）

Torsten 2023-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/1968779-the-loop-is-not-converging-it-is-giving-me-an-infinite-value-it-is-increasing#answer_1240229

移动：Matt J 2023-5-20

在 MATLAB Online 中打开

Why do you think your fixed-point iteration should converge ?

If the absolute values of the eigenvalues of A were all < 1, it would work. But it is not the case:

A = [1 1 2; 1 2 4; 1 2 5];
eig(A)
ans = 3×1
    7.1842
    0.5728
    0.2430

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Torsten 2023-5-20

移动：Matt J 2023-5-20

What do you mean by "make it work" ? It works as you have programmed it and gives you the correct result for the matrix A and the initial vector x: Divergence.

Mahmoud Chawki 2023-5-20