The problem is, very likely, that those "0.0000
" are not exactly 0
. To solve that, choose a tolerance and use it when comparing with 0:
tol = 1e-6;
index_sh = find(abs(eigenvectors(1,:))<tol & abs(eigenvectors(3,:))<tol);
In your code:
for ii = 1:3
if abs(eigenvectors(1,ii))<tol && abs(eigenvectors(3,ii))<tol
index_sh = i
end
end
Or, instead of a tolerance, you could choose the column whose first- and third-row entries are closer to 0:
[~, index_sh] = min(abs(eigenvectors(1,:)) + abs(eigenvectors(3,:)));