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MathGroup Archive 2003

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Re: ParametricPlot - a feature or a bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg39462] Re: ParametricPlot - a feature or a bug?
  • From: peter weijnitz <pewei at algonet.se>
  • Date: Mon, 17 Feb 2003 04:34:07 -0500 (EST)
  • References: <b2nrh3$6oq$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

It seems to have something to do with the way plotting is done, if you have a large
interval (e.g 0-500Pi) Mathematica still use just the default number of plot points,
(50 I think) and straight lines are drawn between the points. So you get the
annulus.
If you increase the number of plotpoints the problem goes away. see below

ParametricPlot[{Cos[t], Sin[t]}, {t, 0, 500 Pi}, AspectRatio -> Automatic,
    PlotPoints -> 1000];

Peter W

Vladimir Bondarenko wrote:

> Hello,
>
> While trying to plot complex parametric plots with large values
> of the parameter I run into a problem which boils down to the
> following simple observation.
>
> a) ParametricPlot[{Cos[t], Sin[t]}, {t, 0, 1 Pi}, AspectRatio -> Automatic];
>
>      A perfect circumference.
>
> b) ParametricPlot[{Cos[t], Sin[t]}, {t, 0, 200 Pi}, AspectRatio -> Automatic];
>
>      Instead of a circumference, not a very wide annulus.
>
> c) ParametricPlot[{Cos[t], Sin[t]}, {t, 0, 500 Pi}, AspectRatio -> Automatic];
>
>      An annulus which width is equal to the radius of the inner
>      circumference.
>
> d) ParametricPlot[{Cos[t], Sin[t]}, {t, 0, 1000 Pi}, AspectRatio -> Automatic];
>
>      A black ring with tiny white spots.
>
> e) ParametricPlot[{Cos[t], Sin[t]}, {t, 0, 10^19 Pi}, AspectRatio -> Automatic];
>
>      A funny net.
>
> f) ParametricPlot[{Cos[t], Sin[t]}, {t, 0, 10^20 Pi}, AspectRatio -> Automatic];
>
>      A segment.
>
> g) ParametricPlot[{Cos[t], Sin[t]}, {t, 0, 10^26 Pi}, AspectRatio -> Automatic];
>
>      Only the axes are shown. There is no graph itself.
>
> Is (at least a part of the shown output) a feature or a bug?
>
> (By the way, before answering why do not try to solve the same
> problems with a couple of other systems? ;-)
>
> Best wishes,
>
> Vladimir Bondarenko
> Mathematical and Production Director
> Symbolic Testing Group
>
> Web  :  No other my site is permitted to me to quote here
>         http://www.CAS-testing.org/  GEMM Project (95% ready)
>
> Email:  vvb at mail.strace.net
> Voice:  (380)-652-447325 Mon-Fri 6 a.m. - 3 p.m. GMT
> ICQ  :  173050619
> Mail :  76 Zalesskaya Str, Simferopol, Crimea, Ukraine



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