MATLAB: Needed FRequency analysis of an EEG signal

eeg analysis

Hi everyone.i am poor about matlab. i need to decompose EEG signals to ALpha,beta,gama… by using FFT. İ do not have a EEG database neither i do not know to use to database. please show me a way. thanks

Best Answer

to be more clear

x=load('EEG_data.txt'); y=fft(x); PS=abs(y).^2; N=length(x); fs=1000; freq=(1:N/2)*fs/N; plot(freq,PS)

Related Solutions

MATLAB: How dwt and wavedec are different ? here why cA1 and C have diffrent values

As you see, dwt() gives only a level 1 DWT, while wavedec gives you multiple levels. But you are correct that wavedec() simply iterates on the approximation coefficients of the previous level as expected.

Why do you say they are different? I do not see it. The first L(1) elements of wavedec should equal cA10 above

chan1 = randn(1024,1);
[cA1,cD1] = dwt(chan1,'db4');
[cA2,cD2] = dwt(cA1,'db4');
[cA3,cD3] = dwt(cA2,'db4');
[cA4,cD4] = dwt(cA3,'db4');
[cA5,cD5] = dwt(cA4,'db4');
[cA6,cD6] = dwt(cA5,'db4');
[cA7,cD7] = dwt(cA6,'db4');
[cA8,cD8] = dwt(cA7,'db4');
[cA9,cD9] = dwt(cA8,'db4');
[cA10,cD10] = dwt(cA9,'db4');
[C,L] = wavedec(chan1,10,'db4');

Now compare:

   C(1:L(1))

with

   cA10

Likewise, compare

C(L(1)+1:L(1)+L(2))

with

cD10

MATLAB: Discrete wavelet transform relation to sampling frequency of the signal

Yes, what you are seeing is that the filters are not perfect bandpass filters, but they are better if they are longer. For example, compare the 'db20'

 Fs = 1e6;
 t = 0:1/Fs:1-1/Fs;
 x = cos(2*pi*50*t);
 [C,L] = wavedec(x,15,'db20');
 details = detcoef(C,L,'cells');
 d14recon = wrcoef('d',C,L,'db20',14);
 plot(d14recon,'k'); % approx 30-60 Hz amplitude nearly 1
 d13recon = wrcoef('d',C,L,'db20',13);
 hold on;
 plot(d13recon,'r');  %look how small the amplitude is

Now compare against the approximation at level 13

   a13recon = wrcoef('a',C,L,'db20',13);
   plot(a13recon,'b');

Best Answer

Related Solutions

MATLAB: How dwt and wavedec are different ? here why cA1 and C have diffrent values

MATLAB: Discrete wavelet transform relation to sampling frequency of the signal

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