Ode45 solver error messages, how do I fix my script?

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Zell Holland
Zell Holland 2015-3-11
回答： Torsten 2015-3-11
Hi, I ran the script below but I got some error messages which I didn't understand. Can someone help me with what the messages mean and point me on how to solve? I can see the problem is to do with PL when it is passed on to the function. Please help.
Error using odearguments (line 92) @(T,X)[(1./X(2)).*(PM.*(PM-X(1)./R))-X(1).*X(3);X(3);(1./IA).*(X(1)-PL-RA.*X(3)-E.*(X(2)-VO))] returns a vector of length 71, but the length of initial conditions vector is 3. The vector returned by @(T,X)[(1./X(2)).*(PM.*(PM-X(1)./R))-X(1).*X(3);X(3);(1./IA).*(X(1)-PL-RA.*X(3)-E.*(X(2)-VO))] and the initial conditions vector must have the same number of elements.
Error in ode45 (line 113) [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...
Error in Flexible_Lung (line 18) [t,xa] = ode45(f,[0 1.5],[760 2.295 -0.12949]);
Pm = 760;
R = 1;
vol_tid = 0.41;
Ra = 0;
w = 2*pi*0.2;
E = 2.8;
Vo = 01;
Ia = 0.0074;
PL = Pm -(R*w).*(0.5*vol_tid).*sin(w.*t) - E*((2.5 - (0.5 * vol_tid)) * cos(w.*t));
f = @(t,x) [ (1./x(2)).*(Pm.*(Pm-x(1)./R)) - x(1).*x(3) ; x(3) ; (1./Ia).*(x(1)-PL - Ra.*x(3) - E.*(x(2)-Vo))];
[t,xa] = ode45(f,[0 1.5],[760 2.295 -0.12949]);
n=Pm-PL
plot(n,xa(:,2))

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回答（1 个）

Torsten
Torsten 2015-3-11
Try
f = @(t,x) [ (1./x(2)).*(Pm.*(Pm-x(1)./R)) - x(1).*x(3) ; x(3) ; (1./Ia).*(x(1)-(Pm -(R*w).*(0.5*vol_tid).*sin(w.*t) - E*((2.5 - (0.5 * vol_tid)) * cos(w.*t))) - Ra.*x(3) - E.*(x(2)-Vo))];
Best wishes
Torsten.

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