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MathGroup Archive 2000

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Re: Random spherical troubles

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25230] Re: [mg25170] Random spherical troubles
  • From: Geoffrey Steeves <gsteeves at gpu.srv.ualberta.ca>
  • Date: Fri, 15 Sep 2000 02:22:00 -0400 (EDT)
  • Organization: University of Alberta
  • References: <8pmmhc$r6a@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

I just happened upon this post, but I think I have a similar question.

In studying whether a sequence of numbers is random, one can construct
what is called a Noise
Sphere(http://mathworld.wolfram.com/NoiseSphere.html).  When I tried this
out, I got a non-uniform distibution of points concentrated along
the verticle axis (phi ~= 0) of the sphere.  Initially I thought that this
was an artifact of my pseudo-random number generator, but I later tried
this out with "real" random numbers and got the same distribution.
Looking at the mapping(as it is shown on the web page):

theta = 2 * Pi * Random[]

phi = Pi * Random[]

r = Sqrt[Random[]]

I thought that the problem was with the distribution in phi.  Is this a
mistake in the map?  Or am I misunderstanding the what a Noise spehere is
supposed to be?  Thanks for the help!


-- 
_______________________________________________________________________________
             Geoff Steeves // University of Alberta Physics //

			http://www.ualberta.ca/~gsteeves
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