Re: Version problem with FindRoot

*To*: mathgroup at smc.vnet.net*Subject*: [mg97190] Re: Version problem with FindRoot*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Sat, 7 Mar 2009 02:41:30 -0500 (EST)*Organization*: Uni Leipzig*References*: <goqug8$ng0$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, system[x_?NumericQ] = {2 w'[n] + f[n]*w[n] == 0, w[n] == v'[n], v[n] == f'[n], w[0] == x, v[0] == 0, f[0] == 0}; gun[x_?NumericQ] := (soln = NDSolve[system[x], {w, v, f}, {n, 0, 10}])[[1, 2, 2]][10.] FindRoot[gun[x] == 1, {x, 1, .5}] work fine. Regards Jens Dr. Robert Kragler wrote: > Hi, > > according to a short note of Alan Hayes, TJM Vol.3, issue 3 (1993 ! ) > there is a 3-liner given for solving boundary problems of ODEs with the= > help of the so-called shooting method. The subsequent program > > system[x_]={2 w'[n]+f[n]* w[n]==0,w[n]==v'[n],v[n]==f= '[n],w[0]==x > ,v[0]==0,f[0]==0 } > > gun:=(soln=NDSolve[system[#],{w,v,f},{n,0,10}])[[1,2,2]][10.]& > > FindRoot[gun[x]==1,{x,1,.5}] (* should give x->0.332058 *) > > works with earlier Mathematica versions 3.0, 4.2 but NOT for 5.2 (which= > I am currently still using in order to finish a manuscript before I wil= l > adapt this to version 7.0). In Mathematica version 6.0 and 7.0 FindRoot= > will work again if the following (version 6 ) system option is used : > > SetSystemOptions["EvaluateNumericalFunctionArgument"->False] > > There is no problem to plot the function gun[x]with Plot[gun[x],{x,0,1}= ] > in Mathematica. > However, in Mathematica version 5.2 FindRoot gives rise to the followin= g > (error) message : > > NDSolve::"ndinnt": "Initial condition x is not a number or a rectangula= r > array of numbers." > > FindRoot::nlnum : The function value {-1.+v?[n][10.`] is not a list of > numbers with > dimensions {1} at {x} = {1.`}.} > > Does anybody have an idea what to do in the case of version 5.2 ? Thank= s > for any suggestion. > > Robert Kragler > > email: kragler at hs-weingarten.de > > >