How to know the step time inside the function that integrated by ode45?
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Mohamed Aburakhis
on 24 Jun 2016
Commented: Walter Roberson
on 25 Jun 2016
I have
x0=1;
[t,x] = ode45(@My_Fun,[0:0.01:10],x0);
and My_Fun is
function x_dot =My_Fun(t, x)
Here %%%
%%I want to know the instantaneous step time %%%
What are t(now) and t(next) %%%
x_dot(1)=2/m-x;
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Accepted Answer
Roger Stafford
on 25 Jun 2016
Edited: Walter Roberson
on 25 Jun 2016
You might be interested in a comment made in
“If tspan contains two elements, [t0 tf], then t contains the internal evaluation points used to perform the integration.” It depends on whether you believe this in a literal sense or that it is merely an "approximate" truth.
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More Answers (1)
Walter Roberson
on 25 Jun 2016
You cannot know the t of the next step. ode45() uses adaptive time steps, so the next time step will depend upon will depend upon the outcome of this step. Also, if your x is not a scalar, then the next ode45 call might have the same time as the current one, but with different boundary conditions (x), so that it can explore the change along the other dimensions.
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Walter Roberson
on 25 Jun 2016
None of the ode* routines permit fixed time step. They do allow setting a guideline for the initial step, and they do allow setting the maximum step, but they do not allow the step size to be fixed.
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