[Eeglablist] Calculating to determine the most dominant frequency in a specific period

[Vibra Lab]

Let me describe my study. A person is given 4 sections (in total around 60
minutes for all sections for each participant). For each section,
participant is given various questions that they need to answer. i.e. it's
like a conversation. Due to the nature of the experiment, the length of
each section for each participant varies. For instance, for section *one *(for
4 participants) there are *4 different lengths* of time window (10 minutes,
15 minutes, 20 minutes, and 25 minutes). Due to that, I have some questions

I tried to look at the archives but it seems that there is no answer for
the problem that I have.

*1. *How can I find what is the most dominant frequency (eg. theta, alpha)
for each section ?

I can plot all types of band via (*Plot  > Channel spectra and map*) by
putting *6, 10, 22, 30 in* column *Frequencies to plot as scalp map* for
instance. But, how do I choose what is the most dominant frequency (out of
4 frequencies in the example above) during specific period / section ? So
that, I can only show one brain figure (eg. brain map figure with 10 Hz)
with statistical consideration.

*2.* I am trying to use the code that is made by Makoto, found it in the
archive , but it seems not working to determine which frequency band that
is dominant in a certain period. I tried the code in different files, but
it showed that low frequency bands have always higher mean amplitude than
high frequency bands (eg. delta's mean amplitude is higher than theta's
one). Why is it so ?

Here's the code from Makoto to find mean amplitude
%%%%%%%%%%%%%%%%%%%
% for your epoched data, channel 2
[spectra,freqs] = spectopo(EEG.data(2,:,:), 0, EEG.srate);

% 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);
betaIdx  = find(freqs>13 & 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))
betaPower  = mean(10.^(spectra(betaIdx)/10))
gammaPower = mean(10.^(spectra(gammaIdx)/10))
%%%%%%%%%%%%%%%%%

Thank you for your help

Best,
Ihshan

if I want to show only one band, considering that is the most dominant or
prominent during specific period,
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