[Eeglablist] exporting averages/ICA across subjects

[Stefan Debener]

Artem,

>1. I was wondering if there is an easy way to export the data for ERP averages
>created in Plot > Sum/Compare ERPs menu. 
>  
>
One way to compute, e.g., a grand mean average, would be to export the 
individual data set averages via gui: File > Export > Data and ICA 
activity to text file > Export ERP average instead of trials. You could 
afterwards create difference waves, grand means etc. by using 
statistical software packages.
However, more convenient would be to compute everything under Matlab. 
The average of an individual EEGLAB data set is given by:

avr = mean(EEG.data,3);

To create a grand mean average across all data sets loaded in EEGLAB, 
the following code should do it:

%%%%%%%%%%
allavr = [];
for i = 1:size(ALLEEG,2)
     allavr(:,:,i) = mean(ALLEEG(i).data,3);
end
gma = mean(allavr,3);
%%%%%%%%%%

You could then use the Matlab 'save' command (type help save for 
details) to export the data into ascii.
Note that the code above requires that all data sets have the same 
number of electrodes and data points, that is,
size of EEG.data must be identical for the first two dimensions. In case 
you have data sets
with bad channels missing, you have to include an additional loop 
dealing with this problem. Let me know
if you need example code how to do it.


Cheers,
Stefan Debener




>I would really appreciate any help.
>
>Thanks,
>
>-Artem Belopolsky
>University of Illinois
>
>
>
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