Help me generate better spectrogram data using Matlab?

Hi everyone

I am trying to generate spectrograms for .mat EEG files to show the breakdown of frequencies over time. I have got a series of spectrograms that look like this but I am not sure how to alter the code so they are more useful. My code currently is this:

% Set the directory containing .mat files

dataDir = 'C:\Users\clloy\Downloads\spectrogram_data_to_use';

% Get a list of all .mat files in the directory

matFiles = dir(fullfile(dataDir, '*.mat'));

% Electrode information (modify as per your electrode configuration)

electrodes = 1:32; % Assuming electrodes are labeled from 1 to 32

% Loop through each file and generate spectrograms for each electrode

for k = 1:length(matFiles)

% Load the .mat file

matFilePath = fullfile(dataDir, matFiles(k).name);

dataStruct = load(matFilePath);

% Extract the Clean_data variable

if isfield(dataStruct, 'Clean_data')

Clean_data = dataStruct.Clean_data;

% Sampling frequency (Hz)

fs = 128; % Sampling rate is 128 Hz

% Size of Clean_data

[numElectrodes, numSamples] = size(Clean_data);

% Loop through each electrode and generate spectrogram

for elecIdx = 1:numElectrodes

% Get data for current electrode

electrodeData = Clean_data(elecIdx, :);

% Generate spectrogram

figure;

spectrogram(electrodeData, 256, [], [], fs, 'yaxis');

% Add title and labels

title(['Spectrogram of Electrode ', num2str(elecIdx), ' - File: ', matFiles(k).name]);

xlabel('Time (s)');

ylabel('Frequency (Hz)');

% Customize y-axis labels for electrodes

ax = gca;

ax.YTickLabel = compose('%.1f', ax.YTick);

% Save the figure as an image file

saveas(gcf, fullfile(dataDir, [matFiles(k).name, '_electrode_', num2str(elecIdx), '_spectrogram.png']));

% Close the figure to avoid excessive memory usage

close(gcf);

end

else

warning('File %s does not contain the variable "Clean_data". Skipping...', matFiles(k).name);

continue;

end

end

Please let me know if theres anything I can do to alter it and make the spectrograms better!

Answer 1

[Star Strider]

I am not certain what problem you’re having. What information do you want to display?

There are actually two Signal Processing Toolbox functions that will produce a spectrogram, one being spectrogram and the other being pspectrum with the 'spectrogram' option. They are similar, however the differ in an important respect. The spectrogram function produces the power spectral density, with units in dB/Hz, while pxpectrum produces the power spectrum, with units in dB.