Re: Stopping NDSolve after a condition is met x times

*To*: mathgroup at smc.vnet.net*Subject*: [mg100332] Re: Stopping NDSolve after a condition is met x times*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Mon, 1 Jun 2009 07:08:25 -0400 (EDT)*References*: <gvtmgr$gg1$1@smc.vnet.net>

Hi, beside the fact that you input miss several brackets, you increment a list k={0} and later k++ and you compare a list k == k++ with it's increment No wonder that in not work. But EOM = x''[t] + 9.8 Sin[x[t]]; x1ic = Pi/2; x1pic = 0; k = 0; sol = NDSolve[{EOM == 0, x[0] == x1ic, x'[0] == x1pic}, {x[t]}, {t, 0, 100}, Method -> {"EventLocator", "Event" -> x[t], "EventAction" :> (k++; If[k > 4, Throw[Null, "StopIntegration"]])}] work fine. Regards Jens James wrote: > I am trying to stop integrating the equations of motion of a simple pendulum after the bob has crossed the vertical a certain number of times. This is the code I have so far. "k" counts the number of times the bob crosses the vertical. > > EOM = x''[t] + 9.8 Sin[x[t]]; > x1ic = Pi/2; > x1pic = 0; > k = {0}; > NDSolve[{EOM == 0, x[0] == x1ic, x'[0] == x1pic}, {x}, {t, 0, 10}, Method -> {EventLocator, "Event" -> {x[t],First[k] - 5}, EventAction :> {k == k++; Print[k],Throw[t1 = t; xt1 = x[t]; xpt1 = x'[t];,StopIntegration"]}}] >