% -------------------------------------------------------------------------------------------------
% QRSdetector.m: QRS detector
% Translation to Matlab of the Mathcad "didactic" version
%
% Input parameters:
% vadx : array of filtered absolute derivate values
% Fs : sampling frequency (in Hertz).
% pth : threshold
%
% Ouput parameters:
% qrsM : matrix of 3 rows:
% QRS supThDer
% QRS maxDer,
% QRS infThDer
%
% Example:
% qrsV=QRSdetector(vadx,fs,0.6);
%
% Copyright (C) 2004 Maurizio Varanini, Clinical Physiology Institute, CNR, Pisa, Italy
%
% 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 "as is" and "as available" in the hope that it will be useful,
% but WITHOUT ANY WARRANTY of any kind; without even the implied warranty of MERCHANTABILITY
% or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License along with this program;
% if not, write to the Free Software Foundation, Inc.,
% 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
%
% For any comment or bug report, please send e-mail to: maurizio.varanini@ifc.cnr.it
% -------------------------------------------------------------------------------------------------
function qrsM=QRSdetector(vadx,Fs,pth)
if (nargin < 2),
error ( 'At least 2 parameters are required' );
elseif (nargin == 2)
pth=0.5;
end
QRSd=0.15*Fs;
maskQT=0.4*Fs;
w02=fix(0.2*Fs);
mD02=meanMaxSc(vadx, w02, 1,1);
w2=fix(2*Fs);
mD2=meanMaxSc(vadx, w2, 1,1);
meaD=mD2;
th=pth*meaD;
j=1;
QRS=0;
maxd=0;
imaxd=1;
iinizio=1;
%ifine=maskQT;
ifine=iinizio;
for i=1:length(vadx)
value=vadx(i);
if(QRS)
if(value < th)
inizio(j)=iinizio;
vimaxd(j)=imaxd;
ifine=i;
fine(j)=i;
maxdc=min(maxd,th*4);
meaD=0.97*meaD + (1-0.97)* maxdc;
th= pth*meaD;
QRS=0;
j=j+1;
elseif(value > maxd)
imaxd=i;
maxd=value;
end
elseif(value > th)
if(i > ifine+maskQT)|(value > th*(2-(i-(ifine+QRSd))/maskQT))
imaxd=i;
iinizio=i;
maxd=value;
QRS=1;
elseif(i < ifine+QRSd)
if(j>1) j=j-1; end
if(value > maxd)
imaxd=i;
maxd=value;
end
QRS=1;
end
end
end
if(j>1)
qrsM=[inizio; vimaxd; fine];
else qrsM=[];
end