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MathGroup Archive 2000

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Re: Plotting complex functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23985] Re: Plotting complex functions
  • From: "Kevin J. McCann" <kevinmccann at home.com>
  • Date: Mon, 19 Jun 2000 01:45:28 -0400 (EDT)
  • References: <8ihvf8$lgj@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Matthijs ,

In order to plot, the function has to produce numbers. Your example below
has two undetermined integration constants; so, the result will not produce
a number. Try the example below. I picked the IC's so that the result would
be complex.

Paste these into a NB

f=y/.DSolve[{y''[t] + y'[t] + y[t] == 0,y[0]==I,y'[0]==1}, y, t]

ParametricPlot[{Re[f[x]], Im[f[x]]}, {x, 0, 10},
   Epilog -> {RGBColor[1, 0, 0], AbsolutePointSize[5],
Point[{Re[f[0.]], Im[f[0.]]}]}];

Cheers,

Kevin

"Matthijs Sypkens Smit" <matthijs at helena.tux.nu> wrote in message
news:8ihvf8$lgj at smc.vnet.net...
> Hi,
>
> How do I make a plot of a complex-valued function, such as y after
> DSolve[y''[t] + y'[t] + y[t] == 0, y, t]
>
> I've tried a ParametricPlot with Re[y[t] and Im[y[t], but either that
> doesn't work or I'm doing it wrong. Any pointers or an example?
>
> --
> Matthijs
>



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