Re: variable initial value in NDSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg99162] Re: variable initial value in NDSolve*From*: dh <dh at metrohm.com>*Date*: Wed, 29 Apr 2009 03:48:22 -0400 (EDT)*References*: <gt6fgd$rli$1@smc.vnet.net>

Hi Stef, if you want a decent answer, you should give a working simple example. Well, why should R[tstart] go to infinity, you say: R[tstart]=0 (note that there is an error it should read == not =). Do you have a discrete System??? Daniel Stef wrote: > Dear Mathematica community, > > I am pretty new with using Mathematica. So, maybe there is a very > obvious solution to my problem that I missed to find out myself. > > I am trying to solve a problem that is setup like that: > > The cost function ec[t] depends on cumulative arrivals R[t]. At a > variable starting point tstart (for which i try to find a cost- > minimizing value in a NMinimize fct), cumulative arrivals are 0. > > NDSolve[{ec'[t]==0,R[tstart]=0}, R[t],t] > > But obviously, the derivative of R[tstart] goes to infinity, which is > why no solution can be found. > > > Thanks for helpful comments! >