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NDSolve EventLocator Method question about the Event option

• To: mathgroup at smc.vnet.net
• Subject: [mg72570] NDSolve EventLocator Method question about the Event option
• From: "Chris Chiasson" <chris at chiasson.name>
• Date: Wed, 10 Jan 2007 02:26:53 -0500 (EST)

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/

• Follow-Ups:
  • Re: NDSolve EventLocator Method question about the Event option
    • From: "Chris Chiasson" <chris@chiasson.name>