spectrogram of a matrix with 32 channels in one graph with color

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Fatemeh Yousef Zadeh 2022-7-6

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1754880-spectrogram-of-a-matrix-with-32-channels-in-one-graph-with-color

编辑： Prajakta Rathod 2023-4-4

采纳的回答： Chunru

Hi all,

I have matrix of EEG data with 32 channels.

I want to create a stacked spectrogram for all 32 channels in one graph to find the hot spots.

I like the x-axis to show the frequency, the y-axis all my channels stacked on one another.

I really appreciate your help.

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Chunru 2022-7-7

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1754880-spectrogram-of-a-matrix-with-32-channels-in-one-graph-with-color#answer_1001890

编辑：Chunru 2022-7-8

在 MATLAB Online 中打开

% generate some data

fs = 500;

x = sin(2*pi*(0:1023)'*(1:32)/fs) + randn(1024, 32);

for i=1:size(x, 2)

[s,f,t] = spectrogram(x(:,i), 256,128,256, fs, 'psd');

if i==1

idx = find(f<=55); % get the freq range

nf = length(idx);

faxis = f(idx);

sall = zeros(nf, size(s,2), 32);

end

sall(:, :, i) = 20*log10(abs(s(idx, :)));

end

imagesc(faxis, [1:32], reshape(sall, nf, [])');

xlabel('f (Hz)');

ylabel('Ch')

[s,f,t] = spectrogram(x(:,i), 256,128,256, fs, 'psd'); return s as short-time-fouriour-transform. 20*log10(abs(s)) is spectrum density estimate (subject to a normalization factor of NFFT and sampling frequency).

if you want to get the ower spectral density or power spectrum direction, you cab use [s,f,t, ps] = spectrogram(x(:,i), 256,128,256, fs, 'psd'); Here ps is the one-sided (for real signal) modified periodogram (a power spectral density estimate).

To recap, the plot above show power spectrum in dB (subject to a constant factor)

doc spectrogram for more details.

Prajakta Rathod 2023-4-4