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MathGroup Archive 1997

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Re: PDF for a LogLogNormal distribution

  • To: mathgroup at smc.vnet.net
  • Subject: [mg7015] Re: PDF for a LogLogNormal distribution
  • From: ghostbit at sprynet.com (Bill Rowe)
  • Date: Thu, 1 May 1997 14:48:59 -0400 (EDT)
  • Organization: none apparent
  • Sender: owner-wri-mathgroup at wolfram.com

In article <5k68eb$ghk at smc.vnet.net>, "David E. Burmaster"
<deb at Alceon.com> wrote:

>Hi
>
>I am stuck. I cannot find a way to use Mma to develop the PDF for a
>probability distribution representing a random variable. Can you pls help
>me??
>
>=-=-=-=-=
>
>Let X be a Normal (or Gaussian) random variable with the usual PDF
>
>        PDF[X]  =       Normal[mu, sig]
>
>                =       (sig Sqrt[2 Pi])^-1 Exp[-0.5 (x-mu)^2 sig^-2]

[rest of post deleted]

I have two suggestions/comments. First, PDFs for many common distributions
are already defined in the standard packages
Statistics`ContinuousDistributions` and Statistics`DiscreteDistributions`.
You could either use these as provided or look at the code and use them as
templates.

Second the snippet of code above won't work as written. First, the
function PDF needs to be specified as PDF[X_] instead of PDF[X]. This is
necessary so that MMa reconizes the X as a pattern to be inserted in the
rhs. Second, the "=" needs to be replaced with the ":=" assignment
operator.
-- 
"Against stupidity, the Gods themselves contend in vain."


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