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

[Divyanshu]

Hi @Catherine,

In order to make the spectrograms better, you can make use of certain options of 'spectrogram()' function like 'windowSize','noverlap'.

You can read more about these options in the following documentation link:

https://www.mathworks.com/help/releases/R2023b/signal/ref/spectrogram.html#d126e200473

Hope it helps!