Re: Odd answer from Mathematica
- To: mathgroup at smc.vnet.net
- Subject: [mg63626] Re: [mg63609] Odd answer from Mathematica
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sun, 8 Jan 2006 03:32:47 -0500 (EST)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
It is not a bug, each returned value is a root. You did not program
Mathematica to find the roots in order.
(soln=Table[{i,FindRoot[BesselJ[0,x]==0,{x,i}]},{i,1,15,2}]);
Chop[BesselJ[0,x]/.soln[[All,2]],10^-15]
{0,0,0,0,0,0,0,0}
Use closer starting estimates
(soln=Table[{i,FindRoot[BesselJ[0,x]==0,{x,3i}]},{i,5}])
{{1, {x -> 2.404825557695773}}, {2, {x -> 5.520078110286309}}, {3, {x ->
8.653727912911013}},
{4, {x -> 11.791534439014281}}, {5, {x -> 14.930917708487787}}}
Or use the standard add-on package NumericalMath`BesselZeros`
Needs["NumericalMath`BesselZeros`"];
soln=Thread[{Range[5],BesselJZeros[0, 5]}]
{{1, 2.404825557695773}, {2, 5.5200781102863115}, {3,
8.653727912911013}, {4, 11.791534439014281},
{5, 14.930917708487787}}
Bob Hanlon
>
> From: "Steeve Brechmann \(schumi\)" <steevebrechmann at yahoo.ca>
To: mathgroup at smc.vnet.net
> Subject: [mg63626] [mg63609] Odd answer from Mathematica
>
>
> Hi everyone,
>
> I was trying to obtain the first five positive roots of the BesselJ[0,x], when
something comes out...
>
> I type :
>
> Table[{i,FindRoot[BesselJ[0,x]==0,{x,i}]},{i,1,15,2}]//TableForm
>
> and Mathematica answer that for x=7, it obtains x->-52,6241 !
>
> Is this a bug ?
>
> Thanks for your help.
>
> Steeve Brechmann "Addict to Mathematica"
>
>
>