[Insight-users] Computation of Eigenvalue and Eigenvector

[Luis Ibanez]

Hi Fucang,

There are several methods for
computing eigen values in VXL.

Since you are interested in the
Hessian matrix, you can take advantage
of the natural symmetry of this matrix
and use the method


    vnl_symmetric_eigensystem

http://www.esat.kuleuven.ac.be/~targetjr/vxl/classvnl__symmetric__eigensystem.html

You will find this method in

   Insight/Utilities/vxl/vnl/algo

The corresponding files are

    vnl_symmetric_eigensystem.h
    vnl_symmetric_eigensystem.txx

This method expects as input a matrix
of float components, and produce as
output a matrix of floats (with the
eigenvectors) and a vector of floats
containing the eigenvalues.

Note that the itk::Matrix derives
from the vnl matrix, so in principle
you can feed itk::Matrices to this
methods.


Regards,


   Luis


-----------------------

Fucang Jia wrote:
> Hi everyone, Hi Luis,
> 
> I want to compute the eigenvalue and eigenvector from 3x3 Hessian 
> Matrix, but I do know how to do using VXL, could you give some hints on 
> this?
> 
> Thanks!
> 
> Fucang
> 
> 
> 
> 
> 
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