[pymvpa] Example Dataset

[Yaroslav Halchenko]

> Well, it looks like the data labels ARE shifted.  When running a
> Bottle vs. Scissors comparison I got 50% accuracy when shifted by 3
> and 58% correct when not shifted.
well 50% vs 58% are within random performance margin -- I would not rely
on them (unlike some of the well-published authors ;-))

> Not convinced by that I ran a Face vs. House classification and got
> 99.5% accuracy with no shift, but only 76.9% accuracy when shifted
> by 3.
that is indeed significant difference ;)

btw - did you try to shift backwards?

> All these tests were with a Linear SVM classifier, so they should be
> stable results.
and default C?

> Even though all signs are pointing to the fact that they were shifted,
> perhaps Michael knows for sure whether they were...

indeed... or may be Yarik who 'recomposed' that data from the one
provided by Haxby (or did you Michael take it from some other source)...
and I don't really remember shifting them. In my analysis (which I've
done long ago) I just dumped first few volumes in a block just "to be
sure".  Dr.Haxby provided us this data some time long ago with each
volume having a label assigned already (iirc), so it might be that they
were already shifted by him.

Sorry for not really shining the light over the whole situation ;-)

> Have a great night,
you please do too

> Per
-- 
Yaroslav Halchenko
Research Assistant, Psychology Department, Rutgers-Newark
Student  Ph.D. @ CS Dept. NJIT
Office: (973) 353-1412 | FWD: 82823 | Fax: (973) 353-1171
        101 Warren Str, Smith Hall, Rm 4-105, Newark NJ 07102
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