Re: FindRoot & NDSolve
- To: mathgroup at smc.vnet.net
- Subject: [mg64672] Re: [mg64650] FindRoot & NDSolve
- From: Pratik Desai <pdesai1 at umbc.edu>
- Date: Sun, 26 Feb 2006 05:07:54 -0500 (EST)
- References: <200602250753.CAA13936@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Takashi Inoue wrote:
>Hi all,
>
>This is my first post to here.
>I have a problem and want your help.
>
>Mathematica 4 did the following calculation with no pleblem,
>while Mathematica 5(.2) cannot do it.
>
>FindRoot[
> (f /.NDSolve[ {D[f[x], {x,1}] - 2 x - a == 0, f[0] == 0}, f, {x, -3, 3}
>][[1]])[2] == 4,
> {a, -10, 10}
> ]
>
I think FindRoot requires a initial guess in 5.X and you need some kind
of looping for your different values of a
Here are two possible alternatives (that I could think of) using DSolve
and NDSolve
(*Using DSolve (more preferable perhaps because of the closed form nature)*)
TableForm[{#,x/.FindRoot[(f/.DSolve[{D[f[x], {x,1}]== 2 x + #, f[0] ==
0}, f,
x][[1,1]])[x]==4,{x,1}]//N}&/@Range[-10,10,1],TableHeadings->{Automatic,{"a","Root
for f[x,a]"}}]
(*Using NDSolve )
Clear[f,x,a]
Table[Reap[NDSolve[{D[f[x], {x,1}]== 2 x + a, f[0] == 0}, f, {x,-3,3},
Method->{EventLocator,
"Event"->f[x]-4,"EventAction":>Sow[{a,x}]}],{a,-10,10,1}]
Hope this helps
Pratik
>Takashi Inoue,Dept. Phys. Sophia University
- References:
- FindRoot & NDSolve
- From: Takashi Inoue <takash-i@sophia.ac.jp>
- FindRoot & NDSolve