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MathGroup Archive 2005

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Re: Plotting a super ellipse

  • To: mathgroup at smc.vnet.net
  • Subject: [mg55185] Re: Plotting a super ellipse
  • From: "Carl K. Woll" <carlw at u.washington.edu>
  • Date: Wed, 16 Mar 2005 05:36:00 -0500 (EST)
  • Organization: University of Washington
  • References: <d0u71l$kno$1@smc.vnet.net> <d1145m$dp2$1@smc.vnet.net> <d13j99$qll$1@smc.vnet.net> <d15rlm$9hq$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Peter,

The OP was interested in plotting a super ellipse. The problem with your 
approach is that the output looks nothing like a super ellipse. The correct 
approach to eliminating the complex numbers that arise when taking a 
negative number to the power 2.5 is to wrap the variables themselves in Abs, 
and not the whole left hand side.

Carl Woll

"Peter Pein" <petsie at arcor.de> wrote in message 
news:d15rlm$9hq$1 at smc.vnet.net...
> JC wrote:
>> On Sun, 13 Mar 2005 10:20:38 +0000 (UTC), Peter Pein <petsie at arcor.de>
>> wrote:
> ...
>>>Hi JC,
>>>
>>>use ImplicitPlot to plot implicitely ;-) and Abs[] to avoid imaginary
>>>Parts (e.g. (-1)^(2.5))
>>>
>>>ImplicitPlot[Abs[(x^2.5) + (y^2.5/1.25^2.5)] == 20., {x, -4, 4}, {y, -5, 
>>>5}]
>>
>>
>> Peter,
>>
>> Thank you very much for taking the time to reply.
>>
>> Your suggestion, while not generating an error message, also did not
>> plot.  This is what it returned:
>>
>> ImplicitPlot[
>>     Abs[x\^2.5` + 0.5724334022399462`\ y\^2.5`] == 20.`, {x, \(-4\),
>>       4}, {y, \(-5\), 5}]\)
>>
>>
>
> Sorry, again and again I forget: I've put <<Graphics` into my init.m
> file. Enter <<Graphics`ImplicitPlot` or just <<Graphics` _before_
> invoking ImplicitPlot[].
> 



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