# Eigenvector Algor differences?

1. Jan 31, 2005

### disillusioned

Hi,

Does different eigenvector algorithm give different result?
eg. using QL with implicit shifts frm (Numerical Recipes) vs Matlab's LAPACK routines?

or anyone knows what method Matlab's LAPACK uses & where i can find the source code in c++?

Are eigenvectors unique?

Thanks!!

2. Feb 1, 2005

### Galileo

I don't know what algoritms you mean and I`m not that familiar with Matlab.

Anyway, different eigenvalues always correspond to linearly independent eigenvectors.
But it is possible to have two linearly independent eigenvectors corresponding to the same eigenvalue.

Hope that helps.

3. Feb 1, 2005

### mikeu

No they're not. Depending on arbitrary choices made while using whatever algorithm you choose you can end up with a different set of eigenvectors than someone else doing the same problem. As a simple example, if [1,2,3] is your eigenvector and [2,4,6]=2[1,2,3] is your friend's, they're both right (assuming one of them is!).

4. Feb 1, 2005

### mathwonk

look, take the identity map. then anything is an eigenvector (except zero). so what do you mean by unique"