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MathGroup Archive 2004

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Re: i dont understand module.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46549] Re: i dont understand module.
  • From: drbob at bigfoot.com (Bobby R. Treat)
  • Date: Mon, 23 Feb 2004 02:15:40 -0500 (EST)
  • References: <c1ampd$460$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

You left out a semicolon.

Needs["Graphics`"];

Module[{}, sol = NDSolve[{a'[t] == -0.1` a[t]
   x[t], b'[
    t] == -0.05` b[t] 
        y[t], x'[t] == -0.1` a[t] x[t] + 0.05` b[t] y[t], y'[
          t] == 0.1` a[t] x[t] - 0.05` b[t] y[t], a[0] == 1, b[
          0] == 1, x[0] == 1, 
            y[0] == 0}, {a, b, x, y}, {t, 0, 
              250}][[1]] ;
  Plot[Evaluate[#[[2]][
          t] & /@ sol], {t, 0, 
            250}, PlotStyle -> Table[Hue[(k + 1)/6], {k, 4}], Frame -> True, 
          Axes -> False, PlotLegend -> (#[[1]] & /@ sol), LegendPosition -> {
          1, -.35}, LegendShadow -> {0, 0}, ImageSize -> 400];]

Bobby

sean_incali at yahoo.com (sean kim) wrote in message news:<c1ampd$460$1 at smc.vnet.net>...
> hello goup. 
> 
> I just don't get this. this code was posted while back by Bob Hanlon. 
> 
> All i did was to flank the routine by a module. i did so to minimize
> memory used. I was hoping that by keepign things local, i can minimize
> the resources used in the routine.
> 
> In[1]:=
> Needs["Graphics`"];
> 
> Module[{},
>   sol=NDSolve[{a'[t]==-0.1` a[t] x[t], b'[t]==-0.05` b[t] y[t], 
>               x'[t]==-0.1` a[t] x[t]+0.05` b[t] y[t], 
>               y'[t]==0.1` a[t] x[t]-0.05` b[t] y[t],
> a[0]==1,b[0]==1,x[0]==1,
>               y[0]==0}, {a,b,x,y},{t,0,250}][[1]]
>         
>         Plot[Evaluate[#[[2]][t]& /@ sol],{t,0,250}, 
>           PlotStyle->Table[Hue[(k+1)/6],{k,4}], Frame->True,
> Axes->False,
>           PlotLegend->(#[[1]]& /@ sol), LegendPosition->{1,-.35},
>           LegendShadow->{0, 0} , ImageSize->400]; 
>   ]
> above fails with the following error. 
> 
> Plot::plnr: sol is not a machine-size real number at t = \
> 0.000010416666666666666`.
> 
> if i flank the module with Do loop, then I get recursion errors
> 
> In[5]:=
> Needs["Graphics`"];
> 
> Do[
>   Module[{},
>     sol=NDSolve[{a'[t]==-0.1` a[t] x[t], b'[t]==-0.05` b[t] y[t], 
>                 x'[t]==-0.1` a[t] x[t]+0.05` b[t] y[t], 
>                 y'[t]==0.1` a[t] x[t]-0.05` b[t] y[t],
> a[0]==1,b[0]==1,
>                 x[0]==1,y[0]==0}, {a,b,x,y},{t,0,250}][[1]]
>           
>           
>           Plot[Evaluate[#[[2]][t]& /@ sol],{t,0,250}, 
>             PlotStyle->Table[Hue[(k+1)/6],{k,4}], Frame->True,
> Axes->False,
>             PlotLegend->(#[[1]]& /@ sol), LegendPosition->{1,-.35},
>             LegendShadow->{0, 0} , ImageSize->400]; 
>     ],
>   {iteration, 10}]
> 
> $RecursionLimit::reclim: Recursion depth of 256 exceeded.
> 
> what's going on here?  and how do i fix it so that i can run it
> automatically?
> 
> thanks all in advance. 
> 
> sean


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