Question about eigen-vector compute value

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,

Answer 1

[Paul]

"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?