[pymvpa] Alternatives to Cross-validation

Jacob Itzhacki jitzhacki at gmail.com
Wed Oct 24 15:15:07 UTC 2012


Please do!

and thank you for all the responses :D

Don't want to come across as lazy but I'm not a master coder at all so
sometimes figuring out what one line of code does can be quite the ordeal,
in my case.

J

On Wed, Oct 24, 2012 at 3:54 PM, Yaroslav Halchenko
<debian at onerussian.com>wrote:

>
> 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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