where is the error in code of Shifted Power Method?

Question

sadiqah aldahan 2022-5-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1719200-where-is-the-error-in-code-of-shifted-power-method

回答： Amanjeet Pani 2022-7-13

Ash=[3 -1 0;-2 6 -2;0 -1 3];

v=zeros(3,10);

vT=zeros(10,3);

v(:,1)=[0;1;0];

vT(1,:)=[0;1;0];

l=6.9996;

Av=zeros(3,10);

AvT=zeros(10,3);

m=zeros(10,1);

error=zeros(10,1);

display('-------------------------------------------------------------------------------------------')

display(' k [v^k]^T [Ashifited v^k]^T mk+1 |error|')

display('-------------------------------------------------------------------------------------------')

for k=1:10

if error(k,1)<0.0005

Ash=Ash-l*eye(3);

Av(:,k)=Ash*v(:,k);

AvT(k,:)=(Av(:,k))';

m(k+1,1)=Av(1,k);

vT(k,:)=(v(:,k))';

error(k+1,1)=abs(m(k+1,1)-m(k,1));

v(:,k+1)=Av(:,k)/m(k+1,1);

l=m(k+1,1);

end

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Jeffrey Clark 2022-6-30

@sadiqah aldahan, you should not use MATLAB commands (e.g., error) as your variable names. See Variable Names and use exist to check. Also don't use display where disp should be used. But your real issue is that when k==3 v(:,k+1)=Av(:,k)/m(k+1,1) divides 0 by 0 which results in NaN being stored in v which in turn results in plenty of NaN in almost every variable.

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Answer 1

Amanjeet Pani 2022-7-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1719200-where-is-the-error-in-code-of-shifted-power-method#answer_1006775

Do not use MATLAB keywords (e.g., error) as your variable names.

To display on the matlab command window use disp().

Also when k==3, v(:,k+1)=Av(:,k)/m(k+1,1) divides 0 by 0 which results in NaN being stored in v which in turn results in plenty of NaN in almost every variable.