Question about eigen-vector compute value

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Felipe Carvajal
Felipe Carvajal 2022-10-7
回答： Paul 2022-10-7
Hello all,
I am programing a code for deformation analysis to geodetic applications. I have a question about my results when I use [U, S, V]=svd() because I need to compute the eigevector belonging to the maximum eigen value. My code is:
clear
clc
o=eye(3);
z=zeros(3);
A= [o -o z z;
z -o o z;
z -o z o;
-o z o z;
o z z -o;
z z o -o];
m = ones(size(A,1),1)*1;
Q = diag(m.*m);
Qxx=pinv(A'*inv(Q)*A)';
Qdd=2*Qxx;
[U,S,V]=svd(Qdd);
ev=U1(1:12,1)
My results are:
0.0000
-0.1037
-0.0870
-0.0511
-0.5908
0.4316
0.1379
0.5637
-0.0650
-0.0868
0.1309
-0.2795
the first term is 6.47407614942793e-17 and this is my doubt, maybe it is a math problem with my matrix (Qdd). I don't know,
I would appreciate any help
Thank you very much,

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回答（1 个）

Paul
Paul 2022-10-7
Ran in:
"I need to compute the eigevector belonging to the maximum eigen value."
Why is SVD being used? Just use eig?
o=eye(3);
z=zeros(3);
A= [o -o z z;
z -o o z;
z -o z o;
-o z o z;
o z z -o;
z z o -o];
m = ones(size(A,1),1)*1;
Q = diag(m.*m);
Qxx=pinv(A'*inv(Q)*A)';
Qdd=2*Qxx;
[V,D] = eig(Qdd,'vector');
D.'
ans = 1×12
0.5000 -0.0000 0.5000 0.5000 0.0000 0.0000 0.5000 0.5000 0.5000 0.5000 0.5000 0.5000
Lot's of repeated eigenvalues. Which one is considered the maximum eigenvalue?

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