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Re: The equivalent of FindRoot for an interpolating function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg37475] Re: [mg37470] The equivalent of FindRoot for an interpolating function
  • From: Sérgio Milo <milo at dmo.fee.unicamp.br>
  • Date: Fri, 1 Nov 2002 01:42:42 -0500 (EST)
  • References: <200210310942.EAA18403@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

      Hi Philip

       In my opinion, can you try this, maybe can resolve your problem.


    sol = NDSolve[{y'[t] == 1 - y[t], y[0] == 0}, y, {t, 0, 20}]
    fy = y /. sol[[1]]

    ANSWER = Table[Max[y[t] /. sol], {t, 0, 0.99, 0.99}]

    ANSWER = Table[Max[y[t] /. sol], {t, 0, 0.9999, 0.9999}]



"Philip M. Howe" wrote:

> Hi Folks,
>
> I wish to find the value of the independent variable in an
> interpolating function that makes the dependent variable assume some
> value of interest.  For example,
>
> sol = NDSolve[{y'[t] == 1-y[t], y[0]==0}, y, {t, 0, 20}]
> fy = y/.sol[[1]]
>
> produces an interpolating function.  I would like to extract the
> value of t that yields a value of 0.99 or 0.9999 (say) for y.  Is
> there a straightforward way of doing this?
>
> Thanks in advance for the help.
>
> Regards,
>
> Phil
> --
> Philip M. Howe
> Program Manager, Stockpile Surety
> Los Alamos National Laboratory
>
> (505) 665-5332
> (505) 667-9498
> Fax: 505-665-5249
> email pmhowe at lanl.gov
> Mail Stop P945



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