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MathGroup Archive 2007

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Re: NDSolve EventLocator Method question about the Event option

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72960] Re: [mg72570] NDSolve EventLocator Method question about the Event option
  • From: "Chris Chiasson" <chris at chiasson.name>
  • Date: Fri, 26 Jan 2007 07:26:39 -0500 (EST)
  • References: <200701100726.CAA10455@smc.vnet.net>

Tom Zeller from WRI sent along this nice tip:

Use
EventLocationMethod"->"LinearInterpolation"

For some reason, in the case on which I am working, this causes the
"subtraction Event" to not be skipped over.

BTW, I think the event I was looking for happened at a discontinuity.

On 1/10/07, Chris Chiasson <chris at chiasson.name> wrote:
> I have a complicated NDSolve command, which I can produce for you if
> you want, that does not seem to "hit" the event I am looking for when
> I use subtraction, but hits the event just fine when I use Less.
>
> Here are the two options:
>
> doesn't work very well (produces NDSolve::evnf):
>
> "Event"->Abs@y@x-height[i[x]]/2
>
> works:
>
> "Event"->Abs@y@x<height[i[x]]/2
>
> height[i[x]] is always a positive number, as is Abs@y@x
>
> Does anyone have any ideas about why this might happen?
>
> P.S. Here is the full (working) Method option:
>
> Method->{"EventLocator","Event"->Abs@y@x<height[i[x]]/2,"EventAction":>Throw[Null,"StopIntegration"]}
>
> --
> http://chris.chiasson.name/
>
>


-- 
http://chris.chiasson.name/


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