Event function Indexing Error

I wrote an event function to stop iteration when the x value of an equation reaches a specific point. It works for the first six initial conditions and then gives me this error:

Index exceeds the number of array elements. Index must not exceed 1.

Error in odezero (line 142)

if any(isterminal(indzc))

The Event function is:

function [value, isterminal, direction] = Xmoon(t, x, mu)
value = x - 1;
isterminal = 1;
direction = 0;
end

and the way i use it in my code is in a for loop that updates my initial conditions twenty times. It lloks like this:

IC = Xu_n;
opts = odeset('RelTol',1e-12,'AbsTol',1e-12,'Events',@Xmoon); % accuracy tolerances
[tspan,xyz_out] = ode45(@ZVC,tspan,IC,opts); % Propogate
x_5 = xyz_out(:,1);
y_5 = xyz_out(:,2);
x_5(end+1:1e4) = nan;
y_5(end+1:1e4) = nan;
x5(:,i) = x_5;
y5(:,i) = y_5;

What is going wrong and how do I fix it?

[Torsten]

We cannot tell the reason without the complete code you are using.

But don't you have to set

opts = odeset('RelTol',1e-12,'AbsTol',1e-12,'Events',@(t,x)Xmoon(t,x,mu)); % accuracy tolerances

instead of

opts = odeset('RelTol',1e-12,'AbsTol',1e-12,'Events',@Xmoon); % accuracy tolerances

?

[Walter Roberson]

@Torsten

Because the trailing parameter mu is not actually used in the event function, it is not necessary to pass it.

Answer 1

[Walter Roberson]

The isterminal vector returned by the event function must be the same length as the value return.

Your IC are probably at least two values, so the x passed to Xmoon will be the same number of values; you then set value = x - 1; which will be the same number of values as IC. But you set isterminal to the scalar 1