53 lines
1.9 KiB
Matlab
53 lines
1.9 KiB
Matlab
function dxdt = derivsecgsyn(t,x,flag,rr,sfint,ti,ai,bi)
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% dxdt = derivsecgsyn(t,x,flag,rr,sampfreq,ti,ai,bi)
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% ODE file for generating the synthetic ECG
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% This file provides dxdt = F(t,x) taking input paramters:
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% rr: rr process
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% sfint: Internal sampling frequency [Hertz]
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% Order of extrema: [P Q R S T]
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% ti = angles of extrema [radians]
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% ai = z-position of extrema
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% bi = Gaussian width of peaks
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% Copyright (c) 2003 by Patrick McSharry & Gari Clifford, All Rights Reserved
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% See IEEE Transactions On Biomedical Engineering, 50(3), 289-294, March 2003.
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% Contact P. McSharry (patrick AT mcsharry DOT net) or
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% G.D. Clifford (gari AT mit DOT edu)
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% This program is free software; you can redistribute it and/or modify
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% it under the terms of the GNU General Public License as published by
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% the Free Software Foundation; either version 2 of the License, or
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% (at your option) any later version.
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%
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% This program is distributed in the hope that it will be useful,
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% but WITHOUT ANY WARRANTY; without even the implied warranty of
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% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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% GNU General Public License for more details.
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%
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% You should have received a copy of the GNU General Public License
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% along with this program; if not, write to the Free Software
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% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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%
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% ecgsyn.m and its dependents are freely availble from Physionet -
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% http://www.physionet.org/ - please report any bugs to the authors above.
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xi = cos(ti);
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yi = sin(ti);
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ta = atan2(x(2),x(1));
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r0 = 1;
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a0 = 1.0 - sqrt(x(1)^2 + x(2)^2)/r0;
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ip = 1+floor(t*sfint);
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w0 = 2*pi/rr(ip);
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fresp = 0.25;
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zbase = 0.005*sin(2*pi*fresp*t);
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dx1dt = a0*x(1) - w0*x(2);
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dx2dt = a0*x(2) + w0*x(1);
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dti = rem(ta - ti, 2*pi);
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dx3dt = - sum(ai.*dti.*exp(-0.5*(dti./bi).^2)) - 1.0*(x(3) - zbase);
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dxdt = [dx1dt; dx2dt; dx3dt];
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