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MathGroup Archive 2002

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Re: Plotting direction fields for a logistic equation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg37213] Re: Plotting direction fields for a logistic equation
  • From: "Steve Luttrell" <luttrell at _removemefirst_westmal.demon.co.uk>
  • Date: Thu, 17 Oct 2002 00:08:31 -0400 (EDT)
  • References: <aokbv7$agi$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Use AspectRatio to control the size of the output:

You get a nice result with PlotVectorField[f[t, y], {t, 0, 80}, {y, 0,
1400}, AspectRatio -> 1];

--
Steve Luttrell
West Malvern, UK

"Ruben Garcia" <rubgb at yahoo.com> wrote in message
news:aokbv7$agi$1 at smc.vnet.net...
> Hi there:
> I've been trying to use PlotVectorField for the
> following differential equation:
> dy/dt = 0.08*y*(1-y/1000)
> but I haven't been successful yet.
> I tried to do the following:
> f[t_, y_] := {1, 0.08*y*(1 - y/1000)}
> <<Graphics`PlotField`
> PlotVectorField[f[t, y], {t, 0, 80}, {y, 0, 1400}];
> but I'm getting a meaningless plot so I'd appreciate
> if someone could tell me what is what I'm doing wrong.
> Thank you very much in advance,
> Ruben
>
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