ODE45, ODE113 How to get the step size in advance?

Of course you can modify the stepsize control in a copy (!) of ode45.m. But this is really unsual and I cannot imagine a good reason to do this. Therefore I still assume, that you need something else.

请先登录，再进行评论。

Answer 3

Floris 2011-9-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/13971-ode45-ode113-how-to-get-the-step-size-in-advance#answer_20695

You can, if you so wish, set a maximum step size using odeset.

See: http://www.mathworks.se/help/techdoc/ref/odeset.html#f92-1039598

But this not really what you want, is it?

4 个评论
显示 2更早的评论隐藏 2更早的评论

Torsten 2017-10-6

Try a stiff solver, e.g. ODE15S.

Best wishes

Torsten.

Jan 2017-10-9

@Nader: The step size is not reduced arbitrarily in the solver, but such, that the error bounds are not exceeded. If you set a minimal step size and the integrator cannot satisfy the local discretization error, it stops with an error message - and it should do so. Fording the integrator to use too large steps leads to inaccurate results. Therefore I disagree, that this "solves" the problem. In opposite: If this works with another tool, it hides the fact, that the problem is not solved, but that you obtain a rough and perhaps completely wrong result.

Maybe your ODE is stiff. Then follow Torsten's suggestion.

ODE integrators and local optimization tools are fragile. You can get a "final value" even if you drive the tools apart from their specifications. Calling this a "result" without an analysis of the sensitivity (measure how the trajectory reacts to small variations of the inputs or parameters) is not scientifically correct. You can find many publications with such mistakes.

请先登录，再进行评论。