Re: DSolve y'[t]==y[t-a]

*To*: mathgroup at smc.vnet.net*Subject*: [mg73263] Re: DSolve y'[t]==y[t-a]*From*: "ben" <benjamin.friedrich at gmail.com>*Date*: Fri, 9 Feb 2007 02:18:58 -0500 (EST)*References*: <eqend4$4e6$1@smc.vnet.net>

Hi Peter, your equation is NOT an ODE, it is an delayed ODE ! That makes a huge difference both in theory and in the numerical treatment. There are add-ons available for Mathematica that solve them, look out for NDelayDSolve.m. Beware that they can behave quite irregular. Why not start with a simple Euler scheme, then you can put in your delay by hand. Bye Ben On 8 Feb., 09:35, Peter Breitfeld <p... at t-online.de> wrote: > I want to solve the equation in the subject. If I enter > DSolve[y'[t] == y[t - a], y[t], t] > I get the error DSolve::ambiguity. > > I triede to define > k[t]=y[t-a] > and to solve the resulting system, but this doesn't work either > because the ambiguity of the independent variable remains. > > Any ideas? > > Gruss Peter > -- > ==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-== > Peter Breitfeld, Bad Saulgau, Germany --http://www.pBreitfeld.de