ecgdemo.m

利用FFT進行心電訊號除噪並截取R波特徵點

%   ECGDEMO    ECG PROCESSING DEMONSTRATION - R-PEAKS DETECTION
%
%              To run the demo successfully "ecgdemomex.dll", ecgdemodata1.mat"
%              and "ecgdemodata2" should be in MatLab's "work"
%              directory

%   We are processing two data samples to demonstrate two different situations
for demo = 1:2:3
    %   Clear our variables
    clear ecg samplingrate corrected filtered1 peaks1 filtered2 peaks2 fresult
    %   Load data sample
    switch(demo)
        case 1,
            plotname = 'Sample 1';
            load ecgdemodata1;
        case 3,
            plotname = 'Sample 2';
            load ecgdemodata2;
    end
    %   Remove lower frequencies
    fresult=fft(ecg);
    fresult(1 : round(length(fresult)*5/samplingrate))=0;
    fresult(end - round(length(fresult)*5/samplingrate) : end)=0;
    corrected=real(ifft(fresult));
    %   Process data and get result
    [filtered1, peaks1, filtered2, peaks2] = ecgdemomex(corrected, samplingrate);
    %   Create figure - stages of processing
    figure(demo); set(demo, 'Name', strcat(plotname, ' - Processing Stages'));
    %   Original input ECG data
    subplot(3, 2, 1); plot((ecg-min(ecg))/(max(ecg)-min(ecg)));
    title('\bf1. Original ECG'); ylim([-0.2 1.2]);
    %   ECG with removed low-frequency component
    subplot(3, 2, 2); plot((corrected-min(corrected))/(max(corrected)-min(corrected)));
    title('\bf2. FFT Filtered ECG'); ylim([-0.2 1.2]);
    %   Filtered ECG (1-st pass) - filter has default window size
    subplot(3, 2, 3); stem((filtered1-min(filtered1))/(max(filtered1)-min(filtered1)));
    title('\bf3. Filtered ECG - 1^{st} Pass'); ylim([0 1.4]);
    %   Detected peaks in filtered ECG
    subplot(3, 2, 4); stem(peaks1);
    title('\bf4. Detected Peaks'); ylim([0 1.4]);
    %   Filtered ECG (2-d pass) - now filter has optimized window size
    subplot(3, 2, 5); stem((filtered2-min(filtered2))/(max(filtered2)-min(filtered2)));
    title('\bf5. Filtered ECG - 2^d Pass'); ylim([0 1.4]);
    %   Detected peaks - final result
    subplot(3, 2, 6); stem(peaks2);
    title('\bf6. Detected Peaks - Finally'); ylim([0 1.4]);
    %   Create figure - result
    figure(demo+1); set(demo+1, 'Name', strcat(plotname, ' - Result'));
    %   Plotting ECG in green
    plot((ecg-min(ecg))/(max(ecg)-min(ecg)), '-g'); title('\bf Comparative ECG R-Peak Detection Plot');
    %   Show peaks in the same picture
    hold on
    %   Stemming peaks in dashed black
    stem(peaks2.*((ecg-min(ecg))/(max(ecg)-min(ecg)))', ':k');
    %   Hold off the figure
    hold off
end