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How to stop ode45 when value reach certain value other-than zero

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I need to stop the ode when y(2) is 0.2 and here is the function I used for the solver but It doesn't work. Any thing wrong with it ?
function [val, terminate, dir]= stopevents(t,y)
val=(y(2)==0.2)-0.5;
terminate=1;
dir=0;
end

Risposte (2)

Jan
Jan il 26 Apr 2018
Modificato: Jan il 26 Apr 2018
An event occurs when value(i) is equal to zero.
function [value, terminate, direction] = stopevents(t, y)
value = y(2) - 0.2;
terminate = 1;
direction = 0;
end
The event function must be smooth. It is extremely unlikely, that the integration meets the point y(2)==0.2 exactly. Therefore your event function does not trigger. In addtion:
val = (y(2)==0.2)-0.5;
replies -0.5 or 0.5, but never 0, which would trigger the event.
By the way: Avoid using "dir" as name of a variable, because this shadows an important built-in function.
  5 Commenti
Dereje
Dereje il 26 Apr 2018
@Jan y(2)-0.2 is not working that is why I asked you but it works for zero.May be something is wrong with my code. @Bjorn Gustavsson Thanks for the detailed clarification.
Bjorn Gustavsson
Bjorn Gustavsson il 27 Apr 2018
@jan: I guess what was meant with y(2) is y(t) for t=2, and not the second component of y

Accedi per commentare.


Bjorn Gustavsson
Bjorn Gustavsson il 26 Apr 2018
You should be able to use the "events handling", look at the code for ballode.m for an example on how to handle it.
HTH

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