[pymvpa] Confusion Matrix for each Node with sphere_gnbsearchlight

[Yaroslav Halchenko]

On Fri, 28 Aug 2015, marco tettamanti wrote:

>    Dear all,
>    is it possible to obtain confusion matrices for all nodes with
>    "sphere_gnbsearchlight", as was suggested before with
>    "sphere_searchlight":

>    slcvte = CrossValidation(clf, partitioner, errorfx=None,
>    postproc=ChainNode([Confusion(labels=fds.UT)]))
>    class KeepConfusionMatrix(Node):
>         def _call(self, fds):
>             out = np.zeros(1, dtype=object)
>             out[0] = (fds.samples)
>             return out

>    slcvte.postproc.append(KeepConfusionMatrix())
>    slght = sphere_searchlight(slcvte, radius=slradius, space='voxel_indices',
>    nproc=4, postproc=mean_sample())
>    slght_map = slght(fds)

quick an possible partial reply

1. "not sure" -- if it pukes then probably not, although judging from
the code I foresaw arbitrary shape of the errorfx output

2. but you could make sphere_gnbsearchlight to return labels (not
errors) and then post-process to get those confusion matrices.  Just
specify  errorfx=None  to it (not to CV).  But you could also try
passing errorfx=ConfusionMatrixError and see how that goes

Please share what you discover/end up with.
mvpa2/tests/test_usecases.py  has more of usecase demos for gnb
searchlights which might come handy

-- 
Yaroslav O. Halchenko, Ph.D.
http://neuro.debian.net http://www.pymvpa.org http://www.fail2ban.org
Research Scientist,            Psychological and Brain Sciences Dept.
Dartmouth College, 419 Moore Hall, Hinman Box 6207, Hanover, NH 03755
Phone: +1 (603) 646-9834                       Fax: +1 (603) 646-1419
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