[pymvpa] Sensitivity analysis fails

[Yaroslav Halchenko]

o o -- you've hit a bug ;) sorry about that

I pushed a fix in my (yoh/master) branch in our git repository,
but what do you run it on (OS?) and from (package, git repository,
source tarball)? would you be able to use pymvpa directly from the
sources in git repository?

More about fix:

since this moment we have 2 separate kinds of analyzers (for
regular mapped or featureselection classifiers), but that is irrelevant
at this user level. But also I've added a state variable
clf_sensitivities for sensitivity analyzers of proxy-classifiers, so
now, in your case I have:

clf=MappedClassifier(LinearCSVMC(), SVDMapper())
sensana=clf.getSensitivityAnalyzer()
sensana.states.enable(['clf_sensitivities'])
sens=sensana(dataset)
print sens.shape
print sensana.clf_sensitivities.shape

and if it is ran as a part of our svdclf example on sample dataset I
see:

Dataset / float32 216 x 530 uniq: 12 chunks 2 labels
(530,)
(216, 1)


so, sens itself is mapped back into original feature space, but I am not
sure what that would actually mean here (interpretations could vary)
since it effectively replaces (IIRC) singular values with
sensitivites, ie changes contribution of each of SVD components.

but sensana.clf_sensitivities is smth easy to make sense of -- that
would be the sensitivities of the 'slave' classifier (ie
LinearCSVMC) which was ran on remapped data... from it you could assess
what dimensions of eigenspace are more influential on classification
than the others

On Thu, 05 Feb 2009, Sergi Costafreda wrote:

>    Hi all
>    Just starting with PyMVPA - thanks for a great tool!
>    I am trying to obtain a sensitivity analysis for a SVD+SVM mapped
>    classifier, by adapting the code of sensanas.py. When I try to run
>    (1) >>> clf=MappedClassifier(LinearCSVMC(), SVDMapper())
>    (2) >>> sensana=clf.getSensitivityAnalyzer()
>    (3) >>> sens=sensana(data)
>    Line (2) returns the following error:
>     >>> "AttributeError: 'MappedClassifier' object has no attribute
>    '_MappedClassifier__clf'"
>    I'd be grateful for any help with this!
>    Best,
>    Sergi

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-- 
Yaroslav Halchenko
Research Assistant, Psychology Department, Rutgers-Newark
Student  Ph.D. @ CS Dept. NJIT
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