[Eeglablist] FFT Transform

[Ibtissem KHOUAJA BENFRADJ]

Hello,I understand that EEG signal (non-periodic and non-stationary) can be decomposed into Fourier series. If not, I do not know the phase and pulse and I have a time signal, I need to extract the spectral amplitude first. I know there are several algorithms that compute the spectral amplitude but I can not find the program that best fits with the data I have.

1. the first point is to calculate the spectral amplitude (by FFT).
2. the second point is to identify the phase and pulse.
3. finally, reconstruct the signal from the data (for this step I'm following the instructions given by Emanuelle Tognoli and it gives very good results.
I need your help, please colleaguesBest regards, Ibti_______________________________________________________________________________Date: Sat, 26 Oct 2013 00:14:36 +0200
Subject: Re: [Eeglablist] FFT Transform
From: saptocondro at googlemail.com
To: ibtissem.khouaja at live.fr

Hallo,
To extract that information, there are many methods:1. using trigonometric identities
http://www.themathpage.com/atrig/trigonometric-identities.htm
http://dx.doi.org/10.1109/TBME.2006.889160v

2. using FFT, and see the real and imaginary parts from each frequency to get the idea of the phase


Best regards,
Condro


On Fri, Oct 25, 2013 at 6:53 PM, Ibtissem KHOUAJA BENFRADJ <ibtissem.khouaja at live.fr> wrote:




Dear all;
I tried this code and it works very well. It's really as I would have. Thank you Emanuelle for your help.
Now, the problem become more and more clear. 
But the aim is to extract unknown information, such as frequency and phase (w and ph).So, from an EEG signal of 500 points which I know only the amplitudes at each moment,
 I need to extract the phase and the frequency and written it as: (for example)Fp1 (t) = A1 sin (W1T + ph1) + B1 sin (W2T + ph2) + C1 sin (W2T ph3 +) + ..... + An sin (wnt + phn).


I hope that you understand me,
best regards, Ibti
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