Problem with ODE45

Hallo, I wrote code on ODE45. I want to record the event at a condition (pasted in the code). The code is as follows.

y1_init = 0; y2_init = 0; ph_init = 0; vy1=0;vy2=2;wz=0;

x_init = [y1_init; y2_init; ph_init]; v_init= [vy1; vy2; wz]; acc_init = [0; 0; 0];

w_init = [x_init; v_init]; wp_init = [v_init; acc_init];

opts = odeset('RelTol',1e-3,'AbsTol',1e-3,'Events',@events);

[t,y,te,ye,ie] = ode45(@expl,[0 30],w_init,[],Mdash,Qdash,Pdash,hdash,s0dash,opts);

 teout = [teout; te];         
  yeout = [yeout; ye];
  ieout = [ieout; ie];

% where Mdash, Qdash,Pdash, hdash,s0dash are matrices I defined earlier.

%Below is the ode function

function dydt = expl(t,y,Mdash,Qdash,Pdash,hdash,s0dash,opts)

dydt = [y(4:6);(Mdash^(-1)*hdash)-(Mdash^(-1)*Qdash*y(1:3))];

end

% below is the vent function

function [value,isterminal,direction] = events(t,y)

value = y(5)-1.9999;

isterminal =1;

direction =0; end

Everything works fine without the definitions of event. But I want to stop the ode at some point (the variable 'value' in event function). But it throws me an error at the main function.

The below is the error.

Error in ode45 (line 78) solver_name = 'ode45';

Output argument "varargout{4}" (and maybe others) not assigned during call to "C:\Program Files\MATLAB\R2012a\toolbox\matlab\funfun\ode45.m>ode45".

Error in Peicewise_ODE_v5 (line 40) [t,y,te,ye,ie] = ode45(@expl,[0 30],w_init,[],Mdash,Qdash,Pdash,hdash,s0dash,opts);

Any Inputs? I don't understand what is the mistake I did.

Answer 1

[Torsten]

Change the following lines:

[t,y,te,ye,ie] = ode45(@(t,y)expl(t,y,Mdash,Qdash,Pdash,hdash,s0dash),[0 30],w_init,opts);

...

function dydt = expl(t,y,Mdash,Qdash,Pdash,hdash,s0dash)

dydt = [y(4:6);(Mdash^(-1)*hdash)-(Mdash^(-1)*Qdash*y(1:3))];

end

Best wishes

Torsten.

[yashwant kolluru]

I did it few minutes back! it works. I still have a short question. I want to compare the value variable (of event function) with an variable from main function.

Something like below

function [value,isterminal,direction] = events(t,y)

value = abs(y(2)-y(1))-s0dash;

isterminal =1;

direction =0;

%Where s0dash is the value from the main and it keeps changing with for loop. I tried passing it to event function but does not work. Can you suggest me, about what can i do know?

[yashwant kolluru]

Apologize, I got the answer.I just changed the definition of the event function.

Anyway! Thanks so much for the help.