[pymvpa] Alternatives to Cross-validation

Yaroslav Halchenko debian at onerussian.com
Wed Oct 24 13:54:41 UTC 2012

On Wed, 24 Oct 2012, MS Al-Rawi wrote:
>    Cross-validation is fine even in this case, you'll just need to rearrange
>    your data in a way to leave-a-set-of-stimuli out, instead of
>    leave-one-run-out. Perhaps PyMVPA has some functionality to do this. 

now it is getting interesting -- I think you got close to what I thought
the question was about:  to investigate the conceptual/true effect of
e.g.  some super-ordinate category (e.g.  animate-vs-inanimate)  you
would like to cross-validate not across functional runs BUT across
sub-ordinate stimuli categories (e.g. train on
humans/reptiles/shoes/scissors to discriminate animacy and
cross-validate into bugs/houses, then continue with another pair to take
out).  And that is what I thought for a moment the question was
about ;)

This all can be (was) done with PyMVPA although would require 3-4
lines of code instead of 1 to accomplish ATM.  If anyone interested I
could provide an example ;)... ?

Yaroslav O. Halchenko
Postdoctoral Fellow,   Department of Psychological and Brain Sciences
Dartmouth College, 419 Moore Hall, Hinman Box 6207, Hanover, NH 03755
Phone: +1 (603) 646-9834                       Fax: +1 (603) 646-1419
WWW:   http://www.linkedin.com/in/yarik        

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