Why noise_signal does not plot correctly? There are the problems in the code to calculate SNR and MSE value .What can I do?

Here is my DATASET

%%
clc;
clear  
close all;
load B02T.mat;

fs=250;
% t = 0.004:1/fs:1;

eeg1 = data{1,1}.X;
channel_1= eeg1(:,1);
ch_1=channel_1(1:2000);
figure;
subplot(2,1,1);
plot(ch_1);

xlabel('Time (s)');
ylabel('Amplitude');
legend('ch1');
title("Plot channel "+1+ " for Structure 1X1");
hold on; 
grid on;

eeg_signal = eeg1(1:2000); % first 2000 samples

subplot(2,1,2);
plot(eeg_signal,'black');
hold on;
grid on;
legend('EEG Signal');
title('Raw EEG Signal');
%%

[IMF, residual, info] = emd(eeg_signal);
imf_count = max(info.NumIMF);
figure;
for i=1:imf_count
    subplot(6,2,i)
    plot(IMF(:,i))
    title("IMF"+i);
end

subplot(6,2,imf_count+1)
plot(residual)
title("Residue");

%%
thresholds = thselect(IMF, 'rigrsure'); % determine threshold for each IMF using universal thresholding
for i = 1:size(IMF, 2)
    IMF(:, i) = wthresh(IMF(:, i), 's', thresholds(i));
end
% Reconstruct denoised signal from thresholded IMFs
denoised_signal = sum(IMF, 2) + residual;
clean_EEG = denoised_signal;
noise_signal = eeg_signal - clean_EEG;
% Plot results
figure;
subplot(3,1,1);
plot(eeg_signal);
title('Original signal');

subplot(3,1,2);
plot(clean_EEG);
legend( 'Denoised signal');
title('Denoised signal');

subplot(3,1,3);
plot(noise_signal);
legend( 'Noisy signal');
title('Noisy signal');
%%
original_signal = eeg_signal; 
reconstructed_signal =clean_EEG;
% Calculate SNR
noise = original_signal - reconstructed_signal;
SNR = 20 * log10(norm(original_signal)/ norm(noise));


% Calculate MSE
%  MSE = mean((norm(original_signal) - norm(reconstructed_signal)).^2);
MSE = immse(norm(original_signal), norm(reconstructed_signal));

disp(['SNR: ', num2str(SNR), ' dB']);
disp(['MSE: ', num2str(MSE)]);

Answer 1

[Cris LaPierre]

You variable noisy_signal is a 2000x2000 array. When you plot it, you get 2000 lines, since each column is treated as a separate data series.

Looking a little earlier in your code, I see that this is because you subtract a 2000x1 vector from a 1x2000 vector. Since the dimensions are not the same, MATLAB uses implicit expansion so that both variables are 2000x2000, and then does an elementwise subtraction.

I suggest transposing one of your variables so that they both have the same size. Something like this:

noise_signal = eeg_signal.' - clean_EEG;

[Komal]

Thank you so much.