hello
it's not yet a firm answer , but this code was first to look at the data and see which criteria could be used to remove outliers
more work needed
infile='Examples.mat';
% read the sample waveform
data = load(infile);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% FFT parameters
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
NFFT = 256; %
NOVERLAP = round(0.75*NFFT);
w = hanning(NFFT); % Hanning window / Use the HANN function to get a Hanning window which has the first and last zero-weighted samples.
% spectrogram dB scale
spectrogram_dB_scale = 80; % dB range scale (means , the lowest displayed level is XX dB below the max level)
for ck = 1:10
x = data.ppg(ck).data;
samples = length(x);
Fs = 1;
time =(0:samples-1)/Fs;
% create a RMS enveloppe of the signal
N = 100; % buffer size for averaging
envelop = sqrt(myslidingavg(abs(x.^2), N));
% plot
figure(3*ck);
plot(time,x,'b',time,envelop,'r');grid
title('input waveform');
% measure zero crossing periods
threshold = mean(envelop);
[ind_crossing,x_crossing,y_crossing]= crossing_V6(x,time,threshold,'linear');
% keep only positive slope crossing points
ind = (1:2:length(ind_crossing));
period_time_interval = [diff(x_crossing(ind))];
figure(3*ck+1);
subplot(2,1,1),plot(time,x,'b',x_crossing(ind),y_crossing(ind),'+r');grid
subplot(2,1,2),plot(period_time_interval,'+r');grid
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% time / frequency analysis : spectrogram demo
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
[sg,fsg,tsg] = specgram(x,NFFT,Fs,w,NOVERLAP);
% FFT normalisation and conversion amplitude from linear to dB (peak)
sg_dBpeak = 20*log10(abs(sg))+20*log10(2/length(fsg)); % NB : X=fft(x.*hanning(N))*4/N; % hanning only
% saturation of the dB range :
% saturation_dB = 60; % dB range scale (means , the lowest displayed level is XX dB below the max level)
min_disp_dB = round(max(max(sg_dBpeak))) - spectrogram_dB_scale;
sg_dBpeak(sg_dBpeak<min_disp_dB) = min_disp_dB;
% plots spectrogram
figure(3*ck+2);
imagesc(tsg,fsg,sg_dBpeak);colormap('jet');
axis('xy');colorbar('vert');grid
title(['Spectrogram / Fs = ' num2str(Fs) ' Hz / Delta f = ' num2str(fsg(2)-fsg(1)) ' Hz ']);
xlabel('Time (s)');ylabel('Frequency (Hz)');
end
