[pymvpa] Cross validation and permutation test

Meng Liang meng.liang at hotmail.co.uk
Fri Mar 11 17:04:49 UTC 2011


Dear Michael,
Thanks very much for your reply! I am using NeuroDebian virtual machine for running PyMVPA. It is built-in software and I don't even know which version of PyMVPA I'm using! How can I find out (sorry for the naive question, I'm just getting to know the NeuroDebian system)?
I'm looking forward to the new full example!
Thanks,Meng

> Date: Fri, 11 Mar 2011 07:43:50 -0500
> From: michael.hanke at gmail.com
> To: pkg-exppsy-pymvpa at lists.alioth.debian.org
> Subject: Re: [pymvpa] Cross validation and permutation test
> 
> On Tue, Mar 08, 2011 at 06:49:59PM +0000, Meng Liang wrote:
> > I was wondering if there is an easy implementation for performing
> > permutation test for a cross validation classification? I saw in the
> > permutation examples provided in the manual permutation can be built
> > in 'TransferError' and the p value can be obtained by '.null_prob'. Is
> > there a similar implementation for CrossValidatedTransferError?  Also,
> > regarding the permutation example in the manual, I ran this example
> > several times and each time I got different p value - sometime very
> > significant sometime non-significant. The difference across runs still
> > exists even when I increase the permutation to 5000. Any explanation?
> 
> Just a quick note (and sorry for the dealy). I'll see whether we can
> finally come up with a proper example for PyMVPA 0.6. The changes from
> 0.5 to 0.6 were partly motivated by the limitations that you are
> pointing out. In 0.6 it should be smoother -- we just need to document
> it. We'll see whether we can post a full example over the weekend.
> 
> Hope that helps,
> 
> Michael
> 
> -- 
> Michael Hanke
> http://mih.voxindeserto.de
> 
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