[Eeglablist] Question regarding fastICA

[Ewa Beldzik]

Dear Mokoto,

Thank you for the interest. I'm not sure if I can enclose the plots here so
I'm gonna use min and max values as a reconstruction criteria.
I have a data x (matrix size 4x1024; ranging <-*3.882;2,466*>)

When I apply following command line in matlab:
*[icasig,A,W]=fastica(x,'numOfIC',4)*
and when I reconstruct x with the formula:
*x4=A*icasig*
I get x4 (matrix size 4x1024; ranging <-*3.882;2,466*>) which presents the
exact plot as x.

Now, when I apply following command line in matlab:
* [icasig2,A2,W2]=fastica(x,'numOfIC',3)*
and then I reconstruct x with:
* x3=A2*icasig2*
I get x3 (matrix size 4x1024; ranging <*-4.453;2,469*>) which presents far
more noise plots then x.

I'm not sure whether I'm not doing something wrong. But if the algorithm
works this way why is it so?

Best regards,
Ewa

On 10 May 2012 21:47, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:

> Dear Ewa,
>
> What do you mean by 'imprecisely'? Or how did you now it is imprecise?
> Please tell us more detail.
>
> Makoto
>
> 2012/5/10 Ewa Beldzik <ewa.beldzik at gmail.com>:
> > Dear all,
> >
> > When applying fastICA algorithm in Matlab to a data consisting of 4
> signals,
> > I have noticed that only when I choose 4 IC to be estimated, the formula
> > A*icasig =X actually works. After choosing 2 or 3 IC the data (X) is
> > reconstructed imprecisely.
> > Could you explain why? I wish to understand the methods fully.
> >
> > Thank you in advance,
> > Ewa
> > PhD student from Cracow
> >
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>
> --
> Makoto Miyakoshi
> JSPS Postdoctral Fellow for Research Abroad
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>
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