Re: NDSolve does not let me to stop

• To: mathgroup at smc.vnet.net
• Subject: [mg30088] Re: NDSolve does not let me to stop
• From: "W. H. Harker" <wharke at sprynet.com>
• Date: Fri, 27 Jul 2001 03:52:23 -0400 (EDT)
• References: <9joa08\$18d\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In article <9joa08\$18d\$1 at smc.vnet.net>, borut at email.si says...
> 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?
>
>
>
> Borut Levart
>
>
>
>
The option StoppingTest->(a condition on x and y) almost does the job (it
overshoots a bit).

```

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