[SciPy-user] First few eigenvectors of a numarray array

Stuart Murdock s.e.murdock at soton.ac.uk
Thu Sep 2 14:50:57 CDT 2004

Hi Dave

David Grant wrote:

> When you say "top 10" do you mean the eigenvalues with the largest or 
> smallest values?

Primarily I would be concerned with the eigenvectors associated with the 
largest eigenvalues as presently
I am interested in Principal Component Analysis of biomolecular 
simulation trajectories. There are ways to approximate
the top eigenvector / eigenvalue, then get the next and so on but I was 
wondering if there were any packages with those
types of algorithms already implemented.



> I would also be interested in knowing if there is any mathematical way 
> of doing this.  Sometimes for example in molecular simulations you 
> only want to calculate the ground state energy, for example, and you 
> don't care about the rest...
> Dave
> Stuart Murdock wrote:
>> Hi
>> I have a 10000 by 10000 square numarray array which I have obtained 
>> using numarray. I need to obtain the first 10 eigenvalues and
>> eigenvectors of this so I dont want to have to calculate all 
>> eigenvectors of the matrix. Is anyone aware of any pythonic packages 
>> which
>> can calculate, lets say, the 10 eigenvectors corresponding to the top 
>> 10 eigenvalues of a numarray array.
>> There are a few functions which calculate all of the eigenvectors e.g.
>> eig
>> eigenvectors
>> but I only want to calculate the top few.
>> Thanks
>> Stuart
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Stuart Murdock Ph.D,
Research Fellow,
Dept. of Chemistry / E-Science,
University of Southampton,
Highfield, Southampton,
SO17 1BJ, United Kingdom

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