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MathGroup Archive 2007

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Re: StoppingTest Constraints in NDSolve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72875] Re: StoppingTest Constraints in NDSolve
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Tue, 23 Jan 2007 05:34:29 -0500 (EST)
  • Organization: The Open University, Milton Keynes, UK
  • References: <ep1stq$g4a$1@smc.vnet.net>

Cham wrote:
> Hi,
> 
> I'm using the NDSolve operation in Mathematica, and I need to add several constraints in the StoppingTest option.  How should I do this ?  More specifically, I want the iteration to stop if :
> 
> (x[t] - 1)^2 + y[t]^2 + z[t]^2 < 0.5
> 
> and 
> 
> (x[t] + 2)^2 + y[t]^2 + z[t]^2 < 0.5
> 
> How to tell this in the StoppingTest option ?
> 

Use RuleDelayed ( :> ) to specify the conditions and a logical and ( && 
) to link both inequalities. For example,

NDSolve[ ... , ...
,StoppingTest :> (x[t] - 1)^2 + y[t]^2 + z[t]^2 <
     0.5 && (x[t] + 2)^2 + y[t]^2 + z[t]^2 < 0.5]

Regards,
Jean-Marc


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