Re: NDSolve differences between mathematica 8 and 9

*To*: mathgroup at smc.vnet.net*Subject*: [mg129586] Re: NDSolve differences between mathematica 8 and 9*From*: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>*Date*: Sat, 26 Jan 2013 01:41:16 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Hello, I am using mathematica 9 and having some problems with a particular expression, but when I tried it on mathematica 8 it worked perfectly. My expression is: NDSolve[{D[T[n,z],n]+i 2 D[T[n,z],{z,2}]+z^2 T[n,z]==0,T[0,z]==1,Derivative[0,1][T][n,5]==0,Derivative[0,1][T][n,0]==0},T,{n,0,5},{z,0,5}] where i is the imaginary number, and on both I had a new window to work on, with nothing having been done previously on it. Mathematica 8 gave me this: {{T-> InterpolatingFunction[{{0.,5.},{0.,5.}},<>]}} and mathematica 9 gave me this: NDSolve::ndnum : Encountered non-numerical value for a derivative at n==0.`.>> Does anyone know what is going on here? I cannot use mathematica 8, as I do not have continual access to that machine. Thank you for your help. Hi, Teresa, It works for me with Mathematica 9: NDSolve[{D[T[n, z], n] + I 2 D[T[n, z], {z, 2}] + z^2 T[n, z] == 0, T[0, z] == 1, Derivative[0, 1][T][n, 5] == 0, Derivative[0, 1][T][n, 0] == 0}, T, {n, 0, 5}, {z, 0, 5}] {{T -> \!\(\* TagBox[ RowBox[{"InterpolatingFunction", "[", RowBox[{ RowBox[{"{", RowBox[{ RowBox[{"{", RowBox[{"0.`", ",", "5.`"}], "}"}], ",", RowBox[{"{", RowBox[{"0.`", ",", "5.`"}], "}"}]}], "}"}], ",", "\<\"<>\"\>"}], "]"}], False, Editable->False]\)}} The only difference is that I used "I" instead of "i". Indeed "I" in Mathematica is the imaginary unit, while "i" is a variable, like any other letter, say, "a", "b", "c" and so on. As long as you did not give it any value, it is understood as an undefined (i.e. non-numerical) variable by Mathematica, and that's what Mathematica reports you: " Encountered non-numerical value...". Have fun, Alexei Alexei BOULBITCH, Dr., habil. IEE S.A. ZAE Weiergewan, 11, rue Edmond Reuter, L-5326 Contern, LUXEMBOURG Office phone : +352-2454-2566 Office fax: +352-2454-3566 mobile phone: +49 151 52 40 66 44 e-mail: alexei.boulbitch at iee.lu