# [Eeglablist] Calculate band power for each single epoch and average them

Steven Dong (HARMAN Connected Services) v-jendo at microsoft.com
Tue May 28 15:47:05 PDT 2019

```Hello

This should be a really easy task, but I am trying to calculate the Fz Theta/Pz Alpha (cognitive workload) for each trial. This is not event-locked, which I am doing 2-second epoch with 1-second overlap on the continuous data.
The following code was adapted and modified based on the code I found online, but it only gave overall power of each frequency band. And I think the Fz Theta/Pz Alpha (cognitive workload) was not accurate.
I would like to learn how I can modify so I can do get the power of alpha and theta from each epoch, get the ration, and them calculate the average.
Or is there another function I should use to achieve this.

Thanks,
Steven Dong

bandFilePath = ‘’

for n = 1:length(ALLEEG)
EEG = ALLEEG(n);
disp(EEG.setname);
EEG=eeg_regepochs(EEG,'recurrence',1,'limits',[-1 1], 'rmbase', NaN);
M = [];
for x = 1:EEG.nbchan
[spectra,freqs] = spectopo(EEG.data(x,y,:), 0, EEG.srate);
% Set the following frequency bands: delta=1-4, theta=4-8, alpha=8-13, beta=13-30, gamma=30-80.
deltaIdx = find(freqs>1 & freqs<4);
thetaIdx = find(freqs>4 & freqs<8);
alphaIdx = find(freqs>8 & freqs<13);
lowerbetaIdx  = find(freqs>13 & freqs<18);
higherbetaIdx = find(freqs>18 & freqs<30);
gammaIdx = find(freqs>30 & freqs<80);
% Compute absolute power.
deltaPower = mean(10.^(spectra(deltaIdx)/10));
thetaPower = mean(10.^(spectra(thetaIdx)/10));
alphaPower = mean(10.^(spectra(alphaIdx)/10));
lowerbetaPower  = mean(10.^(spectra(lowerbetaIdx)/10));
higherbetaPower  = mean(10.^(spectra(higherbetaIdx)/10));
gammaPower = mean(10.^(spectra(gammaIdx)/10));
% Write to matrix M
M(1,x) = deltaPower;
M(2,x) = thetaPower;
M(3,x) = alphaPower;
M(4,x) = lowerbetaPower;
M(5,x) = higherbetaPower;
M(6,x) = gammaPower;
end
fileName = strcat(bandFilePath, EEG.filename(1:end-4),'.csv');
csvwrite(fileName,M);
end

```