Plot PPG signal and absorption coefficient

Table of Contents

Ploting AC and DC component of the PPG signal Ploting the absorption coefficient vs. wavelelngth PPG pulse and the spectrum

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details <https://www.gnu.org/licenses/>.

This code was developed by Miodrag Bolic for the book PERVASIVE CARDIAC AND RESPIRATORY MONITORING DEVICES: https://github.com/Health-Devices/CARDIAC-RESPIRATORY-MONITORING

% Changing the path from main_folder to a particular chapter
main_path=fileparts(which('Main_Content.mlx'));
if ~isempty(main_path)
    %addpath(append(main_path,'/Chapter2'))
    cd (append(main_path,'/Chapter6/PlotPPG'))
    addpath(append(main_path,'/Service'))
end
SAVE_FLAG=0; % saving the figures in a file

Ploting AC and DC component of the PPG signal

clear_all_but('SAVE_FLAG')

load('plethy1.mat')

fs=39;

t=1/fs:1/fs:length(b1)/fs;

f1=figure

f1 =

Figure (1) with properties: Number: 1 Name: '' Color: [0.9400 0.9400 0.9400] Position: [681 559 560 420] Units: 'pixels' Show all properties

plot(t,(100-b1)/100)

ylabel('Normalized signal obtained at the photodetector', 'FontSize', 10)

xlabel('Time (s)', 'FontSize', 10)

ylim([0.9,1.02])

a3=line([0.4 0.4],[0.9 0.9902],'Color','magenta','LineStyle','-.');

a2=line([0.4 0.4],[0.9902 1],'Color','red','LineStyle','--');

%text(0.4,0.945,'\leftarrow DC component')

text(0.4,0.945,{'\leftarrow DC component', ' Non-pulsatile blood', ' De-oxygenated blood', ' Other tissue'})

text(0.4,0.997,'\leftarrow AC component')

title("Pulse at 940 nm")

%saveas(f1, 'Fig6.1b.jpg')

annonation_save('b)',"Fig6.1b.jpg", SAVE_FLAG);

Ploting the absorption coefficient vs. wavelelngth

%Ploting mua

load('spectralLIB.mat')

f2=figure;

ylimreg=ylim;

wav=300:1000;

a1=loglog(wav,muaoxy); M1="Oxygenated Hb";

hold on,

a2=loglog(wav,muadeoxy); M2="Deoxygenated Hb";

a3=line([660 660],ylim,'Color','red','LineStyle','--'); M3="660nm";

a4=line([940 940],ylim,'Color','black','LineStyle','--'); M4="940nm";

legend([a1,a2,a3,a4], [M1, M2,M3,M4]);

xlabel('Wavelength (nm)', 'FontSize', 10)

ylabel('Absorption Coefficient (cm^-1)', 'FontSize', 10)

title('The absorption spectrum')

%saveas(f2, 'Fig6.4.jpg')

annonation_save('',"Fig6.4.jpg", SAVE_FLAG);

PPG pulse and the spectrum

% Generate Data

clear_all_but('SAVE_FLAG')

load('plethy.mat');

a1=rescale1([a;a;a;a;a;a;a;a;a;a]);

fs=77;

T=1/fs;

t=T:T:length(a1)*T;

f3=figure;

plot(t,a1)

title('PPG signal')

xlabel('Time (s)')

ylabel('s_{PPG}(t)')

xlim([0 2.1])

ylim([-0.1 1.1])

a3=line([0.3766 1.3766],[1 1],'Color','magenta','LineStyle','-.');

a2=line([1 2],[0 0],'Color','red','LineStyle','--');

%text(0.4,0.945,'\leftarrow DC component')

text(0.65,0.95,{'\uparrow Peak interval'})

text(1.3,0.05,'\downarrow Onset interval')

%saveas(f3, 'Fig6.6a.jpg')

annonation_save('a)',"Fig6.6a.jpg", SAVE_FLAG);

NyquistF = fs/2;

FResBPM = 0.5; %resolution (bpm) of bins in power spectrum used to determine PR and SNR

N = (60*2*NyquistF)/FResBPM; %number of bins in power spectrum

f4=figure;

n=length(a1);

w = hanning(n);

xw = a1.*w;

N = 4096; %2^nextpow2(n);

Y = fft(xw,N);

P2 = abs(Y/N);

P1 = P2(1:N/2+1);

P1(2:end-1) = 2*P1(2:end-1);

f = fs*(0:(N/2))/N;

plot(f,mag2db(P1))

title('Amplitude Spectrum of PPG pulses')

xlabel('f (Hz)')

ylabel('|S_{PPG}(f)|')

xlim([0,10])

%saveas(f4, 'Fig6.6b.jpg')

annonation_save('b)',"Fig6.6b.jpg", SAVE_FLAG);