Version problem with FindRoot

*To*: mathgroup at smc.vnet.net*Subject*: [mg97161] Version problem with FindRoot*From*: "Dr. Robert Kragler" <kragler at hs-weingarten.de>*Date*: Fri, 6 Mar 2009 05:39:09 -0500 (EST)

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 will 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 following (error) message : NDSolve::"ndinnt": "Initial condition x is not a number or a rectangular 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 ? Thanks for any suggestion. Robert Kragler email: kragler at hs-weingarten.de