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Re: ParametricPlot Problem
*To*: mathgroup at smc.vnet.net
*Subject*: [mg54240] Re: [mg54217] ParametricPlot Problem
*From*: DrBob <drbob at bigfoot.com>
*Date*: Mon, 14 Feb 2005 00:57:55 -0500 (EST)
*References*: <200502140317.WAA14063@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
y[t] is undefined, so what do you expect?
But this works, for instance:
dee = x''[t] + 0.5 x'[t] + x[t] + 0.1 x[t]^2 == Sin[0.1t];
constraints = {x[0] == 1, x'[0] == 0};
sol = x /. First@NDSolve[{dee, constraints}, x, {t, 0, 400}];
ParametricPlot[{sol@t, t}, {t, 0, 200}];
Bobby
On Sun, 13 Feb 2005 22:17:04 -0500 (EST), James <cannonjunk at hotmail.com> wrote:
> Hi,
>
> I'm trying to do a Parametric Plot of a 2nd order differential
> equation:
>
> 1. dee = x''[t] + 0.5 x'[t] + x[t] + 0.1 x[t]^2 == Sin[0.1t];
> 2. constraints = { x[0] == 1, x'[0] == 0};
> 3. sol = NDSolve[ {dee, constraints}, x[t], {t, 0, 400} ];
> 4. ParametricPlot[ {Evaluate[ x[t] /. sol], y [t]}, {t, 0, 200}]
>
> but it keeps telling me
> "ParametricPlot::pptr: "\!\({Evaluate[x[t] /. \[InvisibleSpace]sol]}\)
> does \
> not evaluate to a pair of real numbers at t = 8.333333333333334`*^-6."
> etc.
>
> This is despite the fact that it works if I do a straight "Plot" (ie, I
> just remove the "Parametric" part of 4.)
>
> If anyone can suggest how I might correct this problem I would
> appreciate it a lot since I'm quite out of ideas.
>
> Thanks,
>
> James
> --
> Mathematica 5.0
> UK
>
>
>
>
--
DrBob at bigfoot.com
www.eclecticdreams.net
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