[SciPy-user] Academic Question?

Conor Robinson conor.robinson at gmail.com
Tue Aug 29 11:34:20 CDT 2006


Thanks Aarre,

I have both of those resources, they are good, but I'm really looking
for a study comparing encoding schema.  I've been combing the
University California libraries, however most studies use a "hand
wave" gesture or don't mention how they encode whatsoever.  I've
developed a basic technique for compressing 1ofC, but I would like to
see what others have done.  In bishop around p. 230 he notes you can
use cross entropy with sigmoid for probabilities.

Conor

On 8/28/06, Aarre Laakso <aarre at pair.com> wrote:
>
> Conor Robinson wrote:
> > If one is using 1ofC encoding, what does PCA
> > applied to 1ofC result in?  1ofc is nice if you're trying to get the
> > posterior probability distribution as output (sigmoid single output
> > unit feedforward network),
> > however would this still hold true after applying PCA to reduce input
> > dimensionality?  Does this even make "sense" for 1ofc?  Furthermore,
> > is there any solid literature reviewing encoding schemes for nnets
> > etc?
>
> >From what I've been told, it doesn't make sense to apply PCA to
> categorical variables, although it is a common practice.
>
> If you want the posterior probability distribution at the outputs, then
> I believe you want to use softmax.
>
> The neural nets FAQ http://www.faqs.org/faqs/ai-faq/neural-nets/ has
> some practical advice about encoding, with citations to the literature
> (part 2, "How should categories be encoded?"), as well as some
> recommendations on the literature in general (part 4). If you haven't
> read Bishop (1995), I highly recommend it.
>
> Aarre
>
>
> --
> Aarre Laakso
> http://www.laakshmi.com/aarre/
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