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Re: Re: work only with Performance->Speed

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102841] Re: [mg102838] Re: work only with Performance->Speed
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Sun, 30 Aug 2009 06:05:29 -0400 (EDT)
  • References: <200908291030.GAA00283@smc.vnet.net>
  • Reply-to: drmajorbob at yahoo.com

Interesting... but Mathematica often successfully plots functions which,  
at one point or many, is undefined... simply leaving them out.

Bobby

On Sat, 29 Aug 2009 05:30:45 -0500, Bill Rowe <readnews at sbcglobal.net>  
wrote:

> On 8/27/09 at 6:32 AM, btreat1 at austin.rr.com (DrMajorBob) wrote:
>
>> You have an extra comma (syntax error!), but this fails, too:
>
>> ContourPlot3D[
>> zz (-1 + 1/(xx^2 + yy^2 + zz^2)^(3/2)), {xx, -2, 2}, {yy, -2, 2},
>> {zz, -4, 4}, BoundaryStyle -> Red, RegionFunction -> Function[{x, y,
>> z}, x^2 + y^2 + z^2 >= 1], PerformanceGoal -> "Quality"]
>>
>> "Speed" works, but "Quality" does not. It looks like a bug to me.
>
> I am not so sure this is a bug. The expression becomes 0+0/0 for
> xx=yy=zz=0. When "Speed" is chosen, I assume the algorithm
> samples the expression at far fewer points and likely misses the
> singularity. Conversely, when "Quality" is chosen the
> singularity isn't missed. I would guess the issue is due to the
> presence of this singularity.
>
>



-- 
DrMajorBob at yahoo.com


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