Re: NDSolve does not let me to stop

*To*: mathgroup at smc.vnet.net*Subject*: [mg30078] Re: NDSolve does not let me to stop*From*: "Orestis Vantzos" <atelesforos at hotmail.com>*Date*: Fri, 27 Jul 2001 03:52:16 -0400 (EDT)*Organization*: National Technical University of Athens, Greece*References*: <9joa08$18d$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

What you need is NDSolve's Option "StoppingTest"... StoppingTest:>(Sqrt[x[t1]^2 + y[t1]^2] > 2) is a sample use of it. I strongly recommend using this version: StoppingTest:>(stopT=t; Sqrt[x[t1]^2 + y[t1]^2] > 2) which at the end of the computation holds in stopT the time that you interupted the computation (and is probably not tmax) Orestis "Borut L" <borut at email.si> wrote in message news:9joa08$18d$1 at smc.vnet.net... > Hi, > > You say Mathematica can do wonders, but I just can't figure this one out. > > I'm solving ODE for r[t] = {x[t],y[t]}. Is there a way to stop NDSolve from > going on, when {x[t],y[t]} fullfills a particular constrain (e.g. > Sqrt[x[t1]^2 + y[t1]^2] > 2) and get Interpolating Function object from 0 to > t1? > > If ain't possible this way, how would you solve the problem (with > Mathematica build-in solvers)? It's essentially a very simple > 'one-step-at-a-time' problem (e.g. Rungee Kutta), where you can check on > variables of integration after any time. > > It seems to me, you can check on variables in NDSolve[eqs, {t,tmin,tmax}] > only at tmin and tmax. > > Well? > > > Thanks for your time, > > Borut Levart > > >