[vtkusers] Re: How to get Eigen values and Eigen vectors ?

[Peter.Vanroose at esat.kuleuven.ac.be]

P.Kiran at geind.ge.com wrote:
> I want to do eigen decompostion for a matrix (of order 3x3) to extract the
> principal axes.

The `best' eigenvalue/eigenvector algorithm for general square matrices
is the "RG" algorithm of EISPACK (netlib).  It is an "established" and
well-tested implementation, dating back from 1983 (!) and it is freeware.

There is a c++ wrapper for this algorithm in vnl (part of vxl), namely in
vnl/algo/vnl_real_eigensystem.{h,cxx}, see
http://www.esat.kuleuven.ac.be/~targetjr/vxl/class_vnl_real_eigensystem.html

(And see vnl/tests/test_real_eigensystem.cxx for an example use.)

vxl and vtk can easily be used together.


--                  Peter Vanroose
                    Electrotechnical Department (ESAT/PSI)
                    K.U.Leuven, Belgium.
                    Peter.Vanroose at esat.kuleuven.ac.be