[pymvpa] Searchlight + cross validation & significance

Michael Hanke mih at debian.org
Thu Apr 12 19:11:52 UTC 2012

On Thu, Apr 12, 2012 at 12:29:24PM -0400, Yaroslav Halchenko wrote:
> Searchlight is just a Measure so its chance distribution (per each
> searchlight) and corresponding p-values could be computed the same
> fashion as any other measure, e.g. like in
> http://www.pymvpa.org/examples/permutation_test.html
> done for CrossValidation

Note, however, if you get into really serious MC testing (i.e. only
permuting the respective training portion of the data and _not_ the
testing part) things get a little more complicated.

You basically need to compose a custom MCNullDist estimator that is very
similar to your original searchlight cross-validation, but takes care of
doing the desired constraint permutation inside the cross-validation
inside the searchlight ;-)


Michael Hanke

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