is it possible to change step size of "ode45" ?
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ADNAN KIRAL
el 22 de Nov. de 2018
Comentada: Steven Lord
el 26 de Mayo de 2024
hi
I was wondering can I change step size of "ode45"? If I am not wrong, the default step size taken by Matlab is 1. I want to make 1/2. how can I change without changing many things in Matlab code. If I assign an "option", is that enough? any other options?
thanks
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Jan
el 22 de Nov. de 2018
No, the default step size of ODE45 is not 1. There is not even a default step size. See Torsten's answer: The step size is controlled such, that the provided tolerances are kept.
With using a vector as tspan, you can define the steps in the output, but this is not the internally used step size.
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Torsten
el 22 de Nov. de 2018
Editada: Torsten
el 22 de Nov. de 2018
The stepsize of ode45 is not constant, but chosen such that the error tolerances you prescribe are met. Thus mean step size can only be controlled indirectly by strengthening (-> smaller stepsize) or weakening (-> larger stepsize) the error tolerances RelTol and AbsTol.
Or do you mean changing the time instants when MATLAB supplies the solution ?
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Steven Lord
el 26 de Mayo de 2024
From the description of the tspan input argument on the ode45 documentation page: "If tspan has more than two elements [t0,t1,t2,...,tf], then the solver returns the solution evaluated at the given points. However, the solver does not step precisely to each point specified in tspan. Instead, the solver uses its own internal steps to compute the solution, and then evaluates the solution at the requested points in tspan. The solutions produced at the specified points are of the same order of accuracy as the solutions computed at each internal step." [Emphasis added.]
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