Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2010

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: FindRoot with NDSolve inside of it doesn't work

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111356] Re: FindRoot with NDSolve inside of it doesn't work
  • From: Leonid Shifrin <lshifr at gmail.com>
  • Date: Wed, 28 Jul 2010 07:26:10 -0400 (EDT)

Sam,

This modification will work:

In[31]:=
Clear[f];
f[x0_?NumericQ, y0_?NumericQ] :=
 Module[{sol, x, y},
  (sol = NDSolve[{x'[t] == x[t], y'[t] == y[t], x[0] == x0,
      y[0] == y0}, {x, y}, {t, 0, 1}];
   {x[1], y[1]} /. sol[[1]])]

In[33]:=
 (*f[x0_,y0_]:={x0 Exp[1],y0 Exp[1]};(*Works for this f*)*)
FindRoot[f[x0, y0] == {2.7, 5.4}, {{x0, 1}, {y0, 2}}]


Out[33]= {x0 -> 0.993274, y0 -> 1.98655}

Apart from localizing your variables, the main thing here was to restrict x0
and y0
as input parameters to <f>, to only numeric values, by  appropriate
patterns.

Regards,
Leonid


On Wed, Jul 28, 2010 at 10:54 AM, Sam Takoy <sam.takoy at yahoo.com> wrote:

> Hi,
>
> I think it's completely self-explanatory what I'm trying to do in this
> model example:
>
> f[x0_, y0_] := (
>   sol = NDSolve[{x'[t] == x[t], y'[t] == y[t], x[0] == x0,
>      y[0] == y0}, {x, y}, {t, 0, 1}];
>   {x[1], y[1]} /. sol[[1]]
>   )
>
> (*f[x0_, y0_]:={x0 Exp[1], y0 Exp[1]}; (* Works for this f *) *)
> FindRoot[f[x0, y0] == {2.7, 5.4}, {{x0, 1}, {y0, 2}}]
>
> Can someone please help me fix this and explain why it's not currently
> working?
>
> Many thanks in advance!
>
> Sam
>
>


  • Prev by Date: Re: Student's T Confidence Interval [StudentTCI]
  • Next by Date: Re: Writing to same file from several kernels?
  • Previous by thread: Re: FindRoot with NDSolve inside of it doesn't work
  • Next by thread: Re: FindRoot with NDSolve inside of it doesn't work