*To*: mathgroup@smc.vnet.net*Subject*: [mg11891] Re: NDSolve with delayed terms in equations*From*: Bill Bertram <wkb@ansto.gov.au>*Date*: Fri, 3 Apr 1998 03:45:46 -0500*Organization*: ANSTO*References*: <6fsj92$gi8@smc.vnet.net>

Alban P Tsui wrote: > > I have a set of differential equations. Usually I can solve it with > NDSolve with no problem. However, I do not know how to solve something > like this, say > > x'[t]==y[t]^2+x[t-a] > y'[t]==y[t]x[t] > > with the usuaual intial conditions and a is real and positive. > > x[t-a] is a delayed term. > > What is the best way to tackle this with NDSolve? > > Alban > P.S. Appreciate if you can send solution to me directly as well. While browsing MathSource at the Mathematica web site (www.wolfram.com) today, I happened come across a package that may be what you're after. The package for Mathematica version 3.x is NDelayDSolve.m and can be found in MathSource as Enhancements/Numerical/0209-102. I hope this is useful to you. Cheers, Bill