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MathGroup Archive 2006

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NDSolve:StoppingTest in Algebraic Differential Equations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67071] NDSolve:StoppingTest in Algebraic Differential Equations
  • From: "ben" <benjamin.friedrich at gmail.com>
  • Date: Thu, 8 Jun 2006 04:54:46 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

I discovered a strange behaviour of StoppingTest:

* for an ordinary differential equation everything is fine

  NDSolve[{y'[t] == 1, y[0] == 0}, {y}, {t, 0, 2}, StoppingTest ->
{y[t] > 1}]

* but even for simple algebraic differential equations,

  NDSolve[{y'[t] == 1, x[t] == y[t], y[0] == 0}, {x, y}, {t, 0, 2},
  StoppingTest -> {y[t] > 1}]

  I get an error message

  "Unable to create a NumericalFunction for the expression
  Hold[{y[t] > 1}]
  in the method "EventLocator".

Any suggestions?

Cheers,
Ben


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