Re: NDSolve and Parametric Plot

*To*: mathgroup at smc.vnet.net*Subject*: [mg85450] Re: NDSolve and Parametric Plot*From*: "Steve Luttrell" <steve at _removemefirst_luttrell.org.uk>*Date*: Mon, 11 Feb 2008 06:05:56 -0500 (EST)*References*: <fomjh1$hmn$1@smc.vnet.net>

You need to select the first solution by using [[1]]: repart[t_] := Re[x[t] /. solution[[1]]] impart[t_] := Im[x[t] /. solution[[1]]] Stephen Luttrell West Malvern, UK "Alex Cloninger" <acloninger at wustl.edu> wrote in message news:fomjh1$hmn$1 at smc.vnet.net... > 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? >