Find the max PSD for EEG data

Hi everyone, I'm newbie. I have file 'data.mat' here contain table 'data' ( EEG record at channel AF3 with fs= 128)

I want to find the max PSD for beta,alpha, and theta wave in this signal using pwelch.

Who can help me solve this? thank you very much

Answer 1

[Amith]

Hi Tran,

To find the maximum PSD for beta, alpha, and theta waves in the signal, you can create a function similar to the one shown below:

Assumptions:

The data being analyzed is stored in a file named data.mat and contains a variable Data which holds the signal data.

1. Parameter Definition:

• A Hamming window of length 256 is defined.
• The overlap between segments is set to 128.
• The number of FFT points is set to 512.
• The data is loaded from data.mat.
• The sampling frequency is set to 128 Hz.

2. Power Spectral Density (PSD) Calculation:

• The PSD of the signal is computed using the Welch method (pwelch function).

3. Frequency Bands:

• Identifying the three frequency bands:
• Theta band: 4 to 8 Hz
• Alpha band: 8 to 12 Hz
• Beta band: 12 to 30 Hz

4. Max PSD Calculation:

• The maximum PSD value within each of these bands is found:
• max_psd_theta for the Theta band
• max_psd_alpha for the Alpha band
• max_psd_beta for the Beta band

% Define parameters

window = hamming(256); % Window length
noverlap = 128; % Overlap between segments
nfft = 512; % Number of FFT points
data = load('data.mat');
fs = 128;
% Compute PSD using pwelch
[pxx, f] = pwelch(data.Data, window, noverlap, nfft, fs);

% Find max PSD in each band
theta_band = (f >= 4 & f < 8);
alpha_band = (f >= 8 & f < 12);
beta_band = (f >= 12 & f < 30);

max_psd_theta = max(pxx(theta_band));
max_psd_alpha = max(pxx(alpha_band));
max_psd_beta = max(pxx(beta_band));

% Display results
fprintf('Max PSD in Theta band: %f\n', max_psd_theta);
fprintf('Max PSD in Alpha band: %f\n', max_psd_alpha);
fprintf('Max PSD in Beta band: %f\n', max_psd_beta);

Hope this helps!