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Re: NDSolve and Parametric Plot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85466] Re: NDSolve and Parametric Plot
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Mon, 11 Feb 2008 06:14:19 -0500 (EST)
  • References: <fomjh1$hmn$1@smc.vnet.net>

Alex Cloninger schrieb:
> So I'm trying to run a simple program that will solve this series of differential equations and plot the the x[t] function in the complex plane.  Here's my code.
>
> solution = NDSolve[{x'[t] == 2p[t], x[0] == 2, p'[t] == -2x[t],
    p[0] == Sqrt[-3]}, {x, p}, {t, 0, 2*Ï?}]
>
> repart[t_] := Re[x[t] /. solution]
> impart[t_] := Im[x[t] /. solution]
>
> ParametricPlot[{repart[t], impart[t]}, {t, 0, 2Ï?},
    PlotRange -> {{-2, 2}, {-2,2}}]
>
> For some reason, when I go to plot the curve, I get an error saying 
> ParametricPlot::pptr: {repart[t], impart[t]} does not evaluate to a pair of real numbers at t=2.617993877991494`*^-7
>
> What's going on?  Could someone please help me with this?
>

You should write:
repart:=Re[ x[t]/.solution[[1]] ]
impart:=Im[ x[t]/.solution[[1]] ]

ParametricPlot[{repart,impart},{t,0,2Pi}]



Gruss Peter
-- 
==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de


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