Re: Do loops

*To*: mathgroup at smc.vnet.net*Subject*: [mg3995] Re: Do loops*From*: sherod at boussinesq.Colorado.EDU (Scott Herod)*Date*: Tue, 14 May 1996 02:13:41 -0400*Organization*: University of Colorado at Boulder*Sender*: owner-wri-mathgroup at wolfram.com

I've got code that computes solutions to systems of differential-delay equations using a For loop and restarting things at the ending point of the last run. Below is the loop from an old version which shows how I did it a little more clearly. ======================================================================== delay[num_, cT_, z_] := Block[{T = cT,y}, f[t_] := 0.8; witchargs = {}; For[k = 0, k <= num, k++, sol = NDSolve[{y'[t] + y[t] == f[t] ( 2 - f[t]^z), y[T*k] == f[T*(k+1)]}, y, {t,T*k,T*(k+1)}]; f[t_] := Evaluate[(y /. Flatten[sol])][t-T]; witchargs = {witchargs, t <= T*(k+1), Evaluate[(y /. Flatten[sol])][t]}; ]; g[t_] = Apply[Which, Flatten[witchargs]]; ParametricPlot[{g[t],g[t-T]}, {t,T,T*k}, PlotRange -> All] ]; =========================================================================== Notice that the I.C. in the NDSolve routine is found by substituting into the saved function f[t_] which was creating by shifting t back by the delay time. If you have more questions, please write me. Scott Herod Applied Mathematics University of Colorado, Boulder (sherod at newton.colorado.edu) In article <4ms4ok$58v at dragonfly.wolfram.com>, g.kokkoris at ic.ac.uk (Giorgos Kokkoris) writes: |> Dear fellows, |> I am having a problem in trying to simulate biological invasions using |> Lotka-Volterra dynamics. |> I create a do loop with an NDSolve command at the end of it, in which I have |> to use results from each iteration as my new initial conditions for the next |> run of the do loop. |> Obviously it does not work because I don't know how to do it correctly. |> In each run the results of the next are independent from the results of the |> previous run. |> I can be more specific if I have to. |> Thanks |> Giorgos |> Giorgos D. Kokkoris e-mail: g.kokkoris at ic.ac.uk |> Centre for Population Biology tel: +44-1344-294472 |> Imperial College at Silwood Park fax: +44-1344-873173 |> Ascot, Berks, SL5 7PY |> U.K. ==== [MESSAGE SEPARATOR] ====