NDSolve does not let me to stop

*To*: mathgroup at smc.vnet.net*Subject*: [mg30067] NDSolve does not let me to stop*From*: "Borut L" <borut at email.si>*Date*: Thu, 26 Jul 2001 01:20:03 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

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