function [RSA, saveDiffRwin, saveDiffNum, firstR, lastR] = calculateRSA(troughs, RR, ECG, y);
% troughs contain the time points of each valid respiration trough,
% after adjustments/etc.
% RR contains the time of all R waves in the signal
% ECG is the raw ECG signal, Qd the raw (decimated) respiration signal
% returns RSA, containing the RSA score for each breath
stopPt = 0; startPt = 0; i = 0; j = 0; Rwindow = []; numBeats = 0;
maxBeat = 0; minBeat = 0; minPlace = 0; maxPlace = 0; RSA = [];
saveDiffRwin = []; saveDiffNum = []; firstR = 0;
numBreaths = length(troughs) - 1; % subtract 1 since breath defined between troughs
numRs = length(RR);
for i = 1:numBreaths
stopPt = troughs(i + 1) % get the start and stop time for this breath
startPt = troughs(i)
status = 0;
Rwindow = []; % fill Rwindow with the R points of the beats
for j = 1:numRs % that occured during this breath.
if RR(j) >= startPt & RR(j) < stopPt
if status == 0
Rwindow = [RR(j)]; % 1st beat in window is the 1st AFTER the trough
status = 1;
if firstR == 0 % save this for plotting
firstR = RR(j);
end;
else
Rwindow = [Rwindow, RR(j)];
end;
end;
if RR(j) >= stopPt
Rwindow = [Rwindow, RR(j)]; % last beat is the 1st AFTER the 2nd trough
lastR = RR(j); % save this for plotting also
break;
end;
end;
diffRwindow = diff(Rwindow) % time between all beats in the window
maxBeat = max(diffRwindow); % find longest and shortest beats
minBeat = min(diffRwindow);
numBeats = length(diffRwindow); % find order of max and min beats in the window
saveDiffRwin = [saveDiffRwin, diffRwindow]; % save for plotting
saveDiffNum = [saveDiffNum, (i * ones(1, numBeats))];
for j = 1:numBeats
if maxBeat == diffRwindow(j)
maxPlace = j;
end;
if minBeat == diffRwindow(j)
minPlace = j;
end;
end;
if minPlace < maxPlace
RSA = [RSA, maxBeat - minBeat];
else
RSA = [RSA, 0];
end;
end;
% code to save the variables as external files for checking the calculations
% fid = fopen('RR.txt','w'); fprintf(fid,'%6.2f\n', RR); fclose(fid);
% fid = fopen('troughs.txt','w'); fprintf(fid,'%6.2f\n',troughs); fclose(fid);
% fid = fopen('RSA.txt','w'); fprintf(fid,'%6.2f\n', RSA); fclose(fid);