Re: NIntegrate in NDSolve?

*To*: mathgroup at smc.vnet.net*Subject*: [mg32] Re: NIntegrate in NDSolve?*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Sun, 25 May 2008 02:05:40 -0400 (EDT)*References*: <g18hon$kg7$1@smc.vnet.net>

Hi, and we have answered questions of that type several million times and the archive is full of it, anyway foo[y_?NumericQ] := NIntegrate[z , {z, 0, 1}] NDSolve[{y'[t] == foo[ y[t]], y[0] == 1}, y[t], {t, 0, 1}] work as it should. Regards Jens EcoTheory wrote: > Hello, This is my first Mathematica question ... of many to come, I'm sure. My question is, can you use NIntegrate within NDSolve? My attempts lead to this error: > > NIntegrate::inum : Integrand is non - numerical etc. > > Here is a simple example: > NDSolve[{y'[t] == NIntegrate[z y[t], {z, 0, 1}], y[0] == 1}, y[t], {t, 0, 1}] > > As far as I can tell, Mathematica does not believe that y[t] is a number. But shouldn't the numerical solver give y[t] as a number to NIntegrate? > > Obviously, Mathematica can do this problem easily enough using Integrate instead of NIntegrate, but it cannot integrate the messier double integral in the actual system of ODE's I want to solve. Thanks for suggestions. >