Initial commit

ecgsyn-1.0.0/Matlab/derivsecgsyn.m

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+function dxdt = derivsecgsyn(t,x,flag,rr,sfint,ti,ai,bi)
+% dxdt = derivsecgsyn(t,x,flag,rr,sampfreq,ti,ai,bi)
+% ODE file for generating the synthetic ECG
+% This file provides dxdt = F(t,x) taking input paramters: 
+% rr: rr process 
+% sfint: Internal sampling frequency [Hertz]
+% Order of extrema: [P Q R S T]
+% ti = angles of extrema [radians] 
+% ai = z-position of extrema 
+% bi = Gaussian width of peaks 
+% Copyright (c) 2003 by Patrick McSharry & Gari Clifford, All Rights Reserved  
+% See IEEE Transactions On Biomedical Engineering, 50(3), 289-294, March 2003.
+% Contact P. McSharry (patrick AT mcsharry DOT net) or 
+% G.D. Clifford (gari AT mit DOT edu)
+
+%    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.
+%
+%    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
+% 
+% ecgsyn.m and its dependents are freely availble from Physionet - 
+% http://www.physionet.org/ - please report any bugs to the authors above.
+
+
+xi = cos(ti);
+yi = sin(ti);
+ta = atan2(x(2),x(1));
+r0 = 1;
+a0 = 1.0 - sqrt(x(1)^2 + x(2)^2)/r0;
+ip = 1+floor(t*sfint); 
+w0 = 2*pi/rr(ip);
+
+
+fresp = 0.25;
+zbase = 0.005*sin(2*pi*fresp*t);
+
+dx1dt = a0*x(1) - w0*x(2);
+dx2dt = a0*x(2) + w0*x(1);
+
+dti = rem(ta - ti, 2*pi);
+dx3dt = - sum(ai.*dti.*exp(-0.5*(dti./bi).^2)) - 1.0*(x(3) - zbase);
+
+dxdt = [dx1dt; dx2dt; dx3dt];