Compute DWT coefficients to denoise eeg signal

Question

Now, i want to denoise EEG signal, i have an EEG signal(2048 coefficients) and after run Daubechies4, i also obtain 2048 coefficients, i want to know how to determine details and approximate coefficients on that, and daubechies4 is 4-level daubechies or 1-level with daubechies4 funcion? Thank's so much. Have any tutorials can help me about this?

Answer 1

You can do it in the following way

% Do the Wavelet Transform
[c, l] = wavedec(data, wavelet_level, wavelet_name); % data is a single channel eeg data
% Get the detail and approximate coefficients at each level
for k = 1:wavelet_level
    det_coeff = detcoef(c,l,k); % detail coefficients at level k
    app_coeff = appcoef(c,l,wavelet_name,k) % approximate coefficients at level k
end

Check out the followinf sites

http://www.mathworks.in/help/wavelet/ref/appcoef.html http://www.mathworks.in/help/wavelet/ref/detcoef.html