[Camino-users] question on dteig command and eigendecomposition algorithm

[Alessandro Calamuneri]

Hi camino experts,

using *dteig* command after monotensor fitting with nldt_pos option, I can
get eigenvalues and eigenvectors of my tensors.

To check results I decided to import the same tensor components, output of
*modelfit*, into MATLAB (R2012b) using standard SPM* built-in functions,
and try to get the same eigensystems by using *eig()* command.

Unfortunately I get different results, either for eigenvalues either for
eigenvectors: furthermore, in a certain number of cases, by using matlab
eig() command, I get negative third eigenvalues, whereas this situation is
almost absent when looking at dteig results (I know only semi-positive
definiteness is guaranteed)

Which kind of eigendecomposition algorithm have you implemented?
Is it optimized to work on tensor components?

Best Regards,

Alessandro
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