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MathGroup Archive 2010

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How to manipulate ODE via EventLocator?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg109529] How to manipulate ODE via EventLocator?
  • From: Zachar István <replicatorzed at gmail.com>
  • Date: Mon, 3 May 2010 07:53:55 -0400 (EDT)

Dear Group,

is there a way to manipulate a set of ordinary diff.equations during
NDSolve-runtime, via the EventLocator option? I would like to see for
example that when a specific variable x reaches a certain value at
time t, e.g. x[t] = 10, then its value should be reset to 1 and the
integration should continue from x[t] = 1. Is it possible?

So far I've set up the basics:

sol = NDSolve[{x'[t] == 1.5*x[t], x[0] == 0.1}, {x}, {t, 0, 2},
   Method -> {"EventLocator", "Event" -> x[t] - 1, "EventAction" :>
Throw[end = t, "StopIntegration"]}];
end
Plot[Evaluate[x[t] /. sol], {t, 0, end}, Frame -> True, Axes -> False]

What I'm interested in is what to put inside EventAction to change the
behaviour of the x'[t] function. Any ideas?
Thanks in advance,

Istvan


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