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MathGroup Archive 2000

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Re: insect population dynamics

  • To: mathgroup at
  • Subject: [mg24617] Re: insect population dynamics
  • From: "Seth Chandler" <SChandler at Central.UH.Edu>
  • Date: Fri, 28 Jul 2000 17:23:54 -0400 (EDT)
  • Organization: University of Houston
  • References: <8lj8q0$>
  • Sender: owner-wri-mathgroup at

How about something like this to obtain a visual solution:

        Exp[0.63((1 - #[[1]]/50)) - 0.068#[[2]]], #[[1]]*(1 -
            Exp[-0.068*#[[2]]])} &, ic, iters];


"Mark Hunter" <mhunter at> wrote in message
news:8lj8q0$8rr at
> I'm trying to use mathematica to run insect population models.  I'm new
> to the system, and wolfram support suggested that I post my question
> here.
> The models are simple predator-prey models.  They are non-linear
> simultaneous difference equations.  I've tried using RSolve, but it
> doesn't seem to handle the non-linearity.  Is there a way of using a
> Do-Loop for the same kind of thing?  A simple example of the model that
> I tried is:
> RSolve[{a[n + 1] == a[n]*Exp[0.63((1 - a[n]/50)) - 0.068b[n]],
>       b[n + 1] = a[n]*(1 - Exp[-0.068*b[n]]), a[0] == 25,
>       b[0] == 10}, {a[n], b[n]}, n]
> I want an output for variables a and n at time n, n+1, etc.
> I'd be most grateful for any advice that you can offer, and please don't
> underestimate my current level of ignorance.
> Many thanks,
> Mark Hunter

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