[arpack] eigen_symmetric and the sigma value

Hi, Is there any plan of adding the support of the sigma keyword, like it is done in Matlab (http://www.mathworks.com/access/helpdesk/help/techdoc/ref/** eigs.html) ? It is needed for some algorithms, like the Locally Linear Embedding I'd like to put it the learn scikit. Matthieu -- French PhD student Website : http://matthieu-brucher.developpez.com/ Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn : http://www.linkedin.com/in/matthieubrucher

On Thu, Feb 28, 2008 at 02:35:50PM +0100, Matthieu Brucher wrote:
Is there any plan of adding the support of the sigma keyword, like it is done in Matlab (http://www.mathworks.com/access/helpdesk/help/techdoc/ref/** eigs.html) ?
Yes, it's on my TODO list. It would be good to implement most, if not all, of the shift-invert spectral transform modes along with the generalized eigenproblem modes. The current tickets are http://www.scipy.org/scipy/scipy/ticket/231 and http://www.scipy.org/scipy/scipy/ticket/418 Any help is welcome. Aric

According to the tickets, it seems that the shift are implemented for real matrices, isn't it ? Matthieu 2008/2/28, Aric Hagberg <hagberg@lanl.gov>:
On Thu, Feb 28, 2008 at 02:35:50PM +0100, Matthieu Brucher wrote:
Is there any plan of adding the support of the sigma keyword, like it is done in Matlab ( http://www.mathworks.com/access/helpdesk/help/techdoc/ref/** eigs.html) ?
Yes, it's on my TODO list. It would be good to implement most, if not all, of the shift-invert spectral transform modes along with the generalized eigenproblem modes. The current tickets are http://www.scipy.org/scipy/scipy/ticket/231 and http://www.scipy.org/scipy/scipy/ticket/418
Any help is welcome.
Aric _______________________________________________ Scipy-dev mailing list Scipy-dev@scipy.org http://projects.scipy.org/mailman/listinfo/scipy-dev
-- French PhD student Website : http://matthieu-brucher.developpez.com/ Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn : http://www.linkedin.com/in/matthieubrucher

On Thu, Feb 28, 2008 at 03:01:25PM +0100, Matthieu Brucher wrote:
According to the tickets, it seems that the shift are implemented for real matrices, isn't it ?
There is an alternate interface http://www.scipy.org/scipy/scipy/browser/trunk/scipy/sparse/linalg/eigen/arp... that should solve the shift-invert problem for real (double) matrices. This functionality needs to be folded into the other (arpack.py) interface and extended to work for all matrix types. You might be able to make it work for you until we get to that. Aric

2008/2/28, Aric Hagberg <hagberg@lanl.gov>:
On Thu, Feb 28, 2008 at 03:01:25PM +0100, Matthieu Brucher wrote:
According to the tickets, it seems that the shift are implemented for real matrices, isn't it ?
There is an alternate interface
http://www.scipy.org/scipy/scipy/browser/trunk/scipy/sparse/linalg/eigen/arp... that should solve the shift-invert problem for real (double) matrices. This functionality needs to be folded into the other (arpack.py) interface and extended to work for all matrix types. You might be able to make it work for you until we get to that.
OK, I'll try this, hoping that it behaves like MAtlab's version ;) I'll keep the list informed ! Matthieu -- French PhD student Website : http://matthieu-brucher.developpez.com/ Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn : http://www.linkedin.com/in/matthieubrucher

OK, I'll try this, hoping that it behaves like MAtlab's version ;) I'll keep the list informed !
Matthieu
I tried to use it, but I don't get the same result as Matlab or a standard eigen analysis. I'd like to get the eigenvalues that are strictly greater than zero. Is it possible with one of the speigs option ? Is it planned to add the sigma keyword to the ARPACK_eigs function ? (that's how my problem is solved by Matlab, that's why I'm asking) Matthieu -- French PhD student Website : http://matthieu-brucher.developpez.com/ Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn : http://www.linkedin.com/in/matthieubrucher

On Thu, Feb 28, 2008 at 03:31:42PM +0100, Matthieu Brucher wrote:
I tried to use it, but I don't get the same result as Matlab or a standard eigen analysis. I'd like to get the eigenvalues that are strictly greater than zero. Is it possible with one of the speigs option ?
Is it planned to add the sigma keyword to the ARPACK_eigs function ? (that's how my problem is solved by Matlab, that's why I'm asking)
We'll add that functionality to the eigen_symmetric() and eigen() functions. Aric
participants (2)
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Aric Hagberg
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Matthieu Brucher