how can I distinct the frequency levels in wavelet

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Merve ozdas 2023-8-16

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https://ww2.mathworks.cn/matlabcentral/answers/2009387-how-can-i-distinct-the-frequency-levels-in-wavelet

编辑： Walter Roberson 2023-8-16

Hi, I have an EEG data with 3668 with sampling frequency, and I want to imply wavelet on this but, I could not observe beta exactly.

x = s; % Assign your signal to a variable
Fs = 3668       ; % Sampling frequency
T = 1/Fs; % Sampling period
l = length(x); % Length of signal
% t = (0:l-1)*T; % Time vector
t           = (1:l) * Fs/l;
% d = designfilt ('bandstopiir','FilterOrder',4,'HalfPowerFrequency1',40,'HalfPowerFrequency2',65,'SampleRate',1000); x = filter (d,x);
% Choose a wavelet function
wname = 'db4'; % Daubechies wavelet with four vanishing moments
% Perform wavelet decomposition
[C,L] = wavedec(x,12,wname); % Wavelet decomposition with 12 levels
D5 = wrcoef('d',C,L,wname,5); % Reconstructed signal at level 5//120-230
D6 = wrcoef('d',C,L,wname,6); % Reconstructed signal at level 6//60-120
D7 = wrcoef('d',C,L,wname,7); % Reconstructed signal at level 7//30-60
D8 = wrcoef('d',C,L,wname,8); % Reconstructed signal at level 8//15-30
D9 = wrcoef('d',C,L,wname,9); % Reconstructed signal at level 9//7-15
D10 = wrcoef('d',C,L,wname,10); % Reconstructed signal at level 10//3-7
D11 = wrcoef('a',C,L,wname,10); % Reconstructed signal at level 11/0-3
D11=D11(:)-1643;
% -1683.63
D=(D5+D6)/2
subplot(7,1,3)
plot(t,D10)
% ylim([-0.04,0.04])
title('Theta')
xlabel('Time (s)')
ylabel('Amplitude(mV)')
subplot(7,1,4)
plot(t,D9)

....

Actually I think that 3668/2^10=3.58(approximation function of wrcoef corresponds to delta), 3668/2^10=3.58(detail of wrcoef is theta), 3668/2^9=7.12(detail of wrcoef is alpha), 3668/2^8=14(detail of wrcoef is beta),3668/2^7=28(detail of wrcoef is gamma_low), (D5+D6)/2 between 60-200(gamma high), gamma_high does not matter, but i could not see beta, I do not know, my code is right or wrong, I think that for example 3668/2^8=14(detail of wrcoef is beta) continues through from low to high, if I write minimum value in the function

D8 = wrcoef('d',C,L,wname,8); % Reconstructed signal at level 8//15-30 ,

Can you help me?