Re: insect population dynamics

*To*: mathgroup at smc.vnet.net*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$8rr@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

How about something like this to obtain a visual solution: bughistory[ic_List,iters_]:=NestList[{#[[1]]* Exp[0.63((1 - #[[1]]/50)) - 0.068#[[2]]], #[[1]]*(1 - Exp[-0.068*#[[2]]])} &, ic, iters]; ListPlot[bughistory[{25,10},200],PlotJoined->True] "Mark Hunter" <mhunter at ecology.uga.edu> wrote in message news:8lj8q0$8rr at smc.vnet.net... > 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 >