Error while passing arguments to events function

Question

I have a function called initial which takes an argument funname and performs some integration. I wanted to pass multiple arguments to events function. So I did this:

odeopt=odeset('RelTol',1e-5,'AbsTol',1e-5,'Events',@(t,y) events(t,y,prm,funname));
fun=str2func(funname);
[t,y]=ode15s(fun,[0 3600],z,odeopt,prm);

prm is a structure and funname is a string.

This is the events function:

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

isterminal=1;
direction=0;
v=feval(funname,1,y,prm);
value=~all(v<1e-10);

funname is basically the ode function.

It still says too many input arguments.:

??? Error using ==> initial>@(t,y)events(t,y,prm,funname)
Too many input arguments.

Error in ==> odeevents at 29
  eventValue = feval(eventFcn,t0,y0,eventArgs{:});

Error in ==> ode15s at 263
[haveEventFcn,eventFcn,eventArgs,valt,teout,yeout,ieout] = ...

Error in ==> initial at 10
[t,y]=ode15s(fun,[0 3600],z,odeopt,prm);

Can't be a problem of version (was using 7.6) because this post which addresses this issue was on 2006.

Any Idea?

Answer 1

Since prm is passed as the last argument in ode15s, it will result in the eventArgs cell passing the value to the event handle. In other words, the line

eventValue = feval(eventFcn,t0,y0,eventArgs{:});

is really doing

eventValue = eventFcn(t,y,prm);

So if prm is needed as an extra parameter in the ODE system, just make prm an input in the event handle:

odeopt=odeset(..., @(t,y,prm) events(t,y,prm,funname));

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Also, since the events function is design to locate solutions passing through zeros, the value should be a double such that MATLAB's sign function works properly.