Help needed script frequency
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Carmen Sergiou
on 30 Jun 2021
Commented: Carmen Sergiou
on 30 Jun 2021
Dear Community
I have created a loop to get phase synchronization for frequency range from 4-8 hz, but for some reason the script calculates only the value for 8Hz.
What am I doing wrong?
% phase-based connectivity
load 'EC_I.mat'
% names of the channels you want to compute connectivity between
channel1 = 'Fz';
channel2 = 'F8';
% create complex Morlet wavelet
frequencies = [4:8];
time = -1:1/EEG.srate:1;
half_wavN = (length(time)-1)/2;
all_wavelet = zeros(10, 1001);
for i_frequencies = frequencies
center_freq = i_frequencies ;
wavelet = exp(2*1i*pi*center_freq.*time) .* exp(-time.^2./(2*(4/(2*pi*center_freq))^2))
all_wavelet(i_frequencies,:) = wavelet ;
end
all_phase_synchronization = zeros(1, 1000);
for i_frequencies = frequencies
center_freq = i_frequencies ;
phase_synchronization = abs(mean(exp(1i*(phase_data(2,:)-phase_data(1,:)))));
all_phase_synchronization(i_frequencies,:) = phase_synchronization ;
end
disp([ 'Synchronization between ' channel1 ' and ' channel2 ' is ' num2str(phase_synchronization) '!' ])
All tips would be very helpful!! Thanks in advance,
Carmen
3 Comments
Accepted Answer
Walter Roberson
on 30 Jun 2021
frequencies = [4:8];
nfreq = length(frequencies);
time = -1:1/EEG.srate:1;
half_wavN = (length(time)-1)/2;
all_wavelet = zeros(10, 1001);
for idx = 1 : nfreq
center_freq = frequencies(idx);
wavelet = exp(2*1i*pi*center_freq.*time) .* exp(-time.^2./(2*(4/(2*pi*center_freq))^2));
all_wavelet(idx,:)= wavelet;
end
all_phase_synchronization = zeros(nfreq, size(all_wavelet,2));
for idx = 1 : nfreq
center_freq = frequencies(idx);
phase_synchronization = abs(mean(exp(1i*(phase_data(2,:)-phase_data(1,:)))));
all_phase_synchronization(idx, :) = phase_synchronization ;
end
but you do not use all_wavelet() after you create it. and your phase_synchronization calculation always calculates over the same data and does not use the center_freq information. You also seem to expect it to be a vector rather than having one for each frequency. I suspect that you should not be using a loop there, just
all_phase_synchronization = abs(mean(exp(1i*(phase_data(2,:)-phase_data(1,:)))));
as a single statement with no loop and no initialization to zero needed.
3 Comments
Walter Roberson
on 30 Jun 2021
all_phase_synchronization is exactly the same for all rows because your code does not use the center_freq or idx information at all. Every iteration of the loop only works with phase_data(2,:)-phase_data(1,:) so it is exactly the same calculation every time.
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