[Eeglablist] relationship between no of channels and no of components

[Keith Yoder]

Piotr,
I believe that ICA only returns as many components as runica determines
ought to exist.  Thus, if only 22 of the channels are linearly independent
(perhaps because of electrode bridging), runica will only calculate 22
components.  Another reason may arise from your operating system.  We use
MATLAB R2008a on a 64-bit Intel mac.  Apparently, 64-bit versions of MATLAB
have some problems identifying the number of linearly independent channels.
 In our case, when attempting to identify components from 132 channels, PCA
with runica was only calculating 88 components.
-Keith
--
Research Aide
Belmonte Neuroscience Laboratory
Cornell University

On Tue, Oct 13, 2009 at 9:22 AM, Piotr Jaskowski <jaskowski at vizja.pl> wrote:

>  Dear All,
>
>                I run ICA with 32-channel segmented data. I expected to get
> 32 ICA components. In fact, I’ve got only 22 components and a following
> message:
>
>
>
> Input data size [22,51775] = 22 channels, 51775 frames/nAfter PCA dimension
> reduction,
>
>   finding 22 ICA components using extended ICA.
>
>
>
> Could anybody explain me where the remaining 10 components disappeared?
>
>
>
> Best regards,
>
> Piotr
>
> ---------------------------------------------------
>
> Prof. Piotr Jaskowski, Ph.D.
>
> Department of Cognitive Psychology
>
> University of Finance and Management
>
> Pawia 55, 01-030 Warszawa, Poland
>
> http://cogn.vizja.pl
>
>
>
>
>
> --
>
> Specjalna oferta ksiÿÿek i podrÿcznikÿw: http://oferta.vizja.net.pl
>
>
>
>
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