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Re: Re: How can I "perturbate" a NDSolve

• To: mathgroup at smc.vnet.net
• Subject: [mg102125] Re: [mg102035] Re: [mg102000] How can I "perturbate" a NDSolve
• From: Iván Lazaro <gaminster at gmail.com>
• Date: Thu, 30 Jul 2009 05:31:33 -0400 (EDT)
• References: <200907260754.DAA18931@smc.vnet.net>

Thanks again for all the answers. After studying the examples and
explanations, i could make what i want to.

DrMajorBob was right. A punctual perturbation doesn't change the trayectory,
so I make the perturbation over several time steps. The random work was made
before the NDSolve computation, and I use it to randomly perturbate time
intervals. The following non-real example shows what I say.

Time = 50;
antlist = {};
ant = 2;
Do[
  If[RandomReal[] < 0.2, {
    If[ant <= j <= ant + 3, 5 + 3, {
       AppendTo[antlist, ant];
       Print[ant, " ", j];
       ant = j}]; }],
  {j, 1, Time}];

Equa1[] := x'[t] == Piecewise[
   Flatten[Table[
     {{x[t] - RandomReal[], antlist[[k]] <= t < antlist[[k]] + 3}}, {k, 2,
Length[antlist] - 1}], 1], x[t]]

Maybe it is not "good-looking", but it works well.
Thanks again to everybody.

• References:
  • How can I "perturbate" a NDSolve expresion?
    • From: Iván Lazaro <gaminster@gmail.com>