Re: System of DE's

*To*: mathgroup at smc.vnet.net*Subject*: [mg48187] Re: System of DE's*From*: "Curt Fischer" <crf3 at po.cwru.edu>*Date*: Mon, 17 May 2004 03:21:56 -0400 (EDT)*References*: <c83t0e$mar$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

The built-in Solvers (DSolve, NDSolve, etc.) cannot solve delay differential equations. One way to proceed is to download the NDelayDSolve package by Allan Hayes. Here's a link to the package download: http://library.wolfram.com/infocenter/MathSource/725/ This package will solve delay equations numerically. A difference in this package (and with delay equations in general) is that you need to specify an initial function, defined over the entire range of the longest delay. In NDelayDSolve, you use pure functions for this. See the package documentation for more details. -- Curt Fischer Virgil Stokes wrote: > How can the following system of differential equations be solved in > Mathematica 5.0.0.0? > Note, f3 has a delay in it. > > vars = {x[t], y[t], z[t]}; > k1 = 0.0001; k2 = 0.1; > k3 = 0.0001; > n = 2000; > > f1 = -k1 x[t] y[t] - k3 x[t] z[t]; > f2 = -k2 y[t] + k1 x[t] y[t] + k3 x[t] z[t]; > f3 = k2 (y[t] - y[t - 14]); > inits = {x[0] == n - 10, y[0] == 10, z[0] == 0}; > eqns = {x'[t] == f1, y'[t] == f2, z'[t] == f3}; > > Thanks, > --V. Stokes