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MathGroup Archive 2001

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Re: a couple of gripes

  • To: mathgroup at
  • Subject: [mg29759] Re: [mg29751] a couple of gripes
  • From: Andrzej Kozlowski <andrzej at>
  • Date: Sun, 8 Jul 2001 01:00:05 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

on 01.7.7 3:25 PM, Joshua A. Solomon at J.A.Solomon at wrote:

 > When I evaluate 
> Integrate[f[x]*If[x==y,1,0],{x,-Infinity,Infinity}]
> I don't get 
> f[y].

There is no reason why you should. However the following works:


> When I evaluate 
> PDF[NormalDistribution[x,0],x]
> I don't get 
> 1.

I am not a statistician, but this does not make any sense to me. What is
NormalDistribution[x,0] supposed to be ?  Are you, by any chance, not
confusing the PDF function (which is just the derivative of a CDF function)
with some sort discrete notion of "probability"?

Besides,  we have

b Sqrt[2 Pi]

so even if we decided to define PDF[NormalDistribution[x,0],x] to be
something  it would be most un-natural to choose 1 rather than Infinity.

Andrzej Kozlowski
Toyama International University

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