       • To: mathgroup at smc.vnet.net
• Subject: [mg69703] question about NDelayDSolve
• From: aitor69gonzalez at gmail.com
• Date: Thu, 21 Sep 2006 07:29:36 -0400 (EDT)

```Hello,

I am using NDelayDSolve to solve a set of delay differential equations
that oscillate (see below). I have noticed that the range of
integration (either limit1=400 or limit2=1000) of this function exerts
a big influence on the result. This leads me to ask you, which is the
best result if any? Could you give me some tips on how to use this
function rigorously?
Thank you in advance.

This is the code:

SetDirectory["/your/mathematica/package/directory"];
<< NDelayDSolve.m
a = 4.5; b = 0.23; c = 0.23; k = 33; p0 = 40; Tm = 15; Tp = 2; limit1 =
400; \
limit2 = 1000;
range1 = NDelayDSolve[{p'[t] == a*m[t - Tp] - b*p[t],
m'[t] == k/(1 + (p[t - Tm]^2/p0^2)) - c*m[t]}, {m -> (0 &),
p -> (0 &)}, {t, 0, limit1}, AccuracyGoal -> 0, PrecisionGoal
-> 0];
range2 = NDelayDSolve[{p'[t] == a*m[t - Tp] - b*p[t],
m'[t] == k/(1 + (p[t - Tm]^2/p0^2)) - c*m[t]}, {m -> (0 &),
p -> (0 &)}, {t, 0, limit2}, AccuracyGoal -> 0, PrecisionGoal
-> 0];
Plot[{Evaluate[p[t] /. range1], Evaluate[p[t] /. range2]}, {t, 0,
limit1},
PlotStyle -> {RGBColor[0, 1, 0], RGBColor[1, 0, 0]}]

```

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