function QRS = run_qrsdet_by_seg(ecg,fs,window,thres,ecgType)
% this function is used to run the QRS detector for each window window (non overlapping)
% this is needed because in the case of big artefacts at the begining of
% the record (i.e. where the P&T threshold is computed) it can make the detection fail.
%
% inputs
% ecg: ecg signal
% fs: sampling frequency
% window: size of the window onto which to perform QRS detection (in seconds)
% thres: threshold to be used
% ecgType: 'FECG' or 'MECG'
%
% output
% QRS: QRS location in nb samples (ms)
%
%
% FECG extraction toolbox, version 1.0, Sept 2013
% Released under the GNU General Public License
%
% Copyright (C) 2013 Joachim Behar
% Oxford university, Intelligent Patient Monitoring Group - Oxford 2013
% joachim.behar@eng.ox.ac.uk
%
% Last updated : 02-08-2013
%
% 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 2 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.
% == managing inputs
if nargin<1; error('run_qrsdet_by_seg: wrong number of input arguments \n'); end;
if nargin<2; fs=1000; end;
if nargin<3; window=15; end;
if nargin<4; thres=0.6; end;
if nargin<5; ecgType='FECG'; end;
% == general
segsizeSamp = window*fs; % convert window into nb of samples
NbSeg = floor(length(ecg)/segsizeSamp); % nb of segments
QRS = [];
start = 1;
stop = segsizeSamp;
signForce = 0; % if we want to force the sign of the peak we are looking for
% == core function
try
for ch=1:NbSeg
% for each segment perform QRS detection
QRStemp = 0;
% take +/-1sec around selected subsegment exept for the borders. This
% is in case there is a QRS in between segments -> allows to locate
% them well.
if ch==1
% first subsegment
dTplus = fs;
dTminus = 0;
elseif ch==NbSeg
% last subsegment
dTplus = 0;
dTminus = fs;
else
% any other subsegment
dTplus = fs;
dTminus = fs;
end
% lowering the threshold in case not enough beats are
% detected. Also changed the refractory period to be different between
% mother and foetus. sign of peaks is determined by the sign on the
% first window and then is forced for the following windows.
if strcmp(ecgType,'FECG')
thresTrans = thres;
while length(QRStemp)<20 && thresTrans>0.1
[QRStemp,signForce,~] = qrs_detect(ecg(start-dTminus:stop+dTplus),0.150,thresTrans,fs,[],signForce);
thresTrans = thresTrans-0.1;
end
else
[QRStemp,signForce,~] = qrs_detect(ecg(start-dTminus:stop+dTplus),0.250,thres,fs,[],signForce);
end
NewQRS = (start-1)-dTminus+QRStemp;
NewQRS(NewQRS>stop) = [];
NewQRS(NewQRS<start) = [];
if ~isempty(QRS) && ~isempty(NewQRS) && NewQRS(1)-QRS(end)<0.25*fs
% this is needed to avoid double detection at the transition point
% between two windows
NewQRS(1) = [];
end
QRS = [QRS NewQRS];
start = start+segsizeSamp;
stop = stop+segsizeSamp;
end
catch ME
for enb=1:length(ME.stack); disp(ME.stack(enb)); end;
QRS = [1000 2000];
end
end