Signal Processing Asked by joe kid on October 24, 2021
I am new in DSP, but I am trying to process EEG data to decompose into the bands, theta, alpha, and others.
The raw data is processed:
The using the bandpass function of Matlab it is bandpassed.
delta = [0.1 4];
theta = [4 8];
alpha = [8 12];
beta = [12 30];
gamma = [30 45];
bands = [delta; theta; alpha; beta; gamma];
fs = 128; % sampling freq of the EEG
% choosing a segment of data
time = 2 ; % secs
fs = 128;
size_t = fs * time;
sample_filt = af3(1:size_t); % AF3, an EEG node
% band passing
eeg_bands = {};
for i = 1 : size(bands, 1)
eeg_bands{i} = bandpass( sample_filt, bands(i,:), fs);
end
% code to plot
I performed bandpass for samples of different time duration, however, I saw the time duration changes the amplitudes of bands at the start and end in gamma and beta (high frequency bands).
here, I plot three figures. Figure 1 of long 5 secs (for me, visually it is reasonable). Figure 2, of 2 secs of duration and notice the start of signals beta and gamma are noisy.
Taking in account EEG, I ask you,
I thank you in advance, please feel free to comment, I need to be right to extract features in the next step.
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