[Eeglablist] runica

[Sven Hoffmann]

Hi all,

i have a question concerning the new eeglab version.
i have run runica (and also pop_runica) several times, and if i remove 
one or several components, or rereference to average reference, and then 
recompute runica, the same number of components is computed as before. 
This appeared a bit strange to me since the removal of components or 
average reference reduces the rank of the data. Having a look at the 
revision history i found that the data is converted to double precision 
prior  infomax calculation. So i tried the rank() matlab function of 
matlab and it seems that applying it to single or double precision leads 
to different results. Below is the difference in the pop_runica code:

pop_runica (v5.03)                                                   
482         tmprank = rank(tmpdata(:,1:min(3000, 
size(tmpdata,2))));                     

pop_runica(v6.0b)
555        tmprank = rank(double(tmpdata(:,1:min(3000, 
size(tmpdata,2)))));   

May be this is a bug? I would suggest to convert the data to double 
precision following rank() calculation.

Cheers, Sven.




 

-- 
Sven Hoffmann

Institute for Occupational Physiology at the University of Dortmund (IfADo)
(Leibniz Research Centre for Working Environment and Human Factors)
Ardeystr. 67
D-44139 Dortmund
Phone: +49-231-1084-338
Fax: +49-231-1084-401
E-mail: shoffmann at ifado.de
Web: http://www.ifado.de/neurophys