Re: Octave ode45 vs. Matlab ode45

[Torsten]

On 14.06.2013 21:22, Jeffrey wrote:
> I'm getting different results from Octave's ode45 than from Matlab's. I
> also need to vary ode45's tolerance level, but I'm getting the following
> messages:
> 
> warning: Option "RelTol" will be ignored if fixed time stamps are given
> warning: Option "AbsTol" will be ignored if fixed time stamps are given
> 
> What do these messages mean? How do I properly set the tolerance? The
> documentation I can find indicates that 'time stamps' have to do with the
> time stamps of my source files. So not related to ode solving.
> 
> Here is how I set the tolerance:
> tol=1e-8;
> options=odeset('Stats','on');
> options=odeset(options,'AbsTol',tol);
> options=odeset(options,'RelTol',tol);
> [t,u1]=ode45(@(t,y) f(t,y,beta), t; [u0;v0], options);
> 

I guess "time stamps" means that you have a vector of time instances as
time parameter t instead of an interval ([t_begin, t_end]). In the
latter case, ode45 can chose the grid points in order to match the
tolerances. For a time vector, this grid is fixed.

Torsten