Can't take a value from an InterpolatingFunction.

*To*: mathgroup at smc.vnet.net*Subject*: [mg13622] Can't take a value from an InterpolatingFunction.*From*: iioannou at u.washington.edu (I. Ioannou)*Date*: Fri, 7 Aug 1998 03:08:23 -0400*Organization*: University of Washington, Seattle*Sender*: owner-wri-mathgroup at wolfram.com

Hi all, I've set up and solved a system of two differential equations, according to the following prescription; solution = NDSolve[{r'[t] == .....equation1......, p'[t] == .....equation2......, r[0] == 0.,p[0] == p0}, {r, p}, {t, 0, 0.2}, MaxSteps \[Rule] 300000, Method \[Rule] Automatic] All has worked very nicely. However, I need now to take the value of r at t=0.2 and I can't seem to be able to do it. I should point out that the Book suggestion r[0.2] /. % doesn't work, because the above statement is within a For loop and is run many times. (to collect various r[0.2] values that come out) So, it's within one big cell. The error reported sais that solution is not a valid lookup table. Well, from what I understand, it's a set (?) of two InterpolatingFunctions. If I knew what kind of entity solution is, I might be able to figure how to instruct Mathematica to let me access r[0.2]. Any help appreciated, thanks, John -- Ioannis I Ioannou phone: (206)-543-1372 g-2 group, Atomic Physics fax: (206)-685-0635 Department of Physics University of Washington e-mail: iioannou at u.washington.edu