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MathGroup Archive 2001

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Re: Drawing a Washer, Polar Plot Question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg29736] Re: [mg29728] Drawing a Washer, Polar Plot Question
  • From: BobHanlon at aol.com
  • Date: Thu, 5 Jul 2001 06:08:01 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 2001/7/4 6:56:32 PM, rlove at antispam.neosoft.com writes:

>I have a polar plot of my data that lookes the way I want.  Now
>I want to add a grey "washer" shaped exclusion zone on top of 
>the plot.  I see there is a nice Disk two dimensional graphics
>object that is almost what I want.  It draws a filled in circle 
>centered on {x,y} of radius r.  What I want is some thing that
>draws a filled in circle between r1 and r2, centered on {x,y}.
>Is there some way I can do this easily?  I've tried combining two
>Disks of different colors and sizes but no luck.
>

One approach:

Needs["Graphics`Graphics`"];
Needs["Graphics`Colors`"];
Needs["Graphics`InequalityGraphics`"];

doughnut[{x0_, y0_}, r1_?Positive, r2_?Positive, opts___?OptionQ] := 
    Module[{x, y, rminSq = Min[r1, r2]^2, rmax = Max[r1, r2], rmaxSq}, 
      rmaxSq = rmax^2; 
      InequalityPlot[
        rminSq<=((x-x0)^2+(y-y0)^2)<=rmaxSq, 
        {x,x0-rmax,x0+rmax}, {y,y0-rmax,y0+rmax} ]];

DisplayTogether[
    PolarPlot[{4/(2+Cos[t]),4 Cos[t]-2},
      {t,0,2 Pi}, 
      PlotStyle -> Red], 
    doughnut[{-1, -1}, 2, 3]];


Bob Hanlon
Chantilly, VA  USA


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