[Eeglablist] Data and ICA Activity Values

[Arnaud Delorme]

> Hi, I have exported my filtered data out using Export > Data and ICA
> Activity  /Weight Matrix / Inverse weight matrix / Events
> 
> Could someone tell me what do the values in each text file mean for:
> 
> 1) Data and ICA Activity
> 2) Weight Matrix
> 3) Inverse weight matrix

I would refer you to these tutorial pages for ICA

https://sccn.ucsd.edu/wiki/Chapter_09:_Decomposing_Data_Using_ICA
http://arnauddelorme.com/ica_for_dummies/

> 4) Events
> 
> I'm also missing headers such as Delta TP7,Alpha TP7,Beta TP7 etc. for the
> " Data and ICA Activity". Why is that so?

This is because it is the raw data. EEGLAB does not allow exporting frequency decomposition of data. For this, you need to use the menu Plot > Channel Spectra and maps. Then to export the value within specific frequency bands, you will need to write a small Matlab script. 

Below is an example of a script for a continuous dataset

freqNames = { 'theta' 'alpha' 'beta' };
freqRange = [4 6; % theta
              9 11; % alpha
              18 22]; % beta
[power, freqs] = pop_spectopo(EEG, 1, [0 EEG.pnts/EEG.srate], 'EEG' , 'plot','off');
for iFreq = 1:size(freqRange,1)
    [~,begFreq] = min(abs(freqs-freqRange(iFreq,1)));
    [~,endFreq] = min(abs(freqs-freqRange(iFreq,2)));
    power2(iFreq,:) = mean(power(:,begFreq:endFreq),2)';
end

fid = fopen('alpha_power.csv', 'w');
fprintf(fid, ',%s', freqNames{:});
for iChan = 1:size(power2,2)
fprintf(fid, '\n%s', EEG.chanlocs(iChan).labels);
fprintf(fid, ',%f', power2(:, iChan)');
end
fclose(fid);

And you get a document you can open in a spreadsheet program like Excel. Perhaps, someone could package this code into an EEGLAB plugin if that’s useful to people.

Best wishes,

Arno