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st: RE: RE: Bessel

From   "Nick Cox" <>
To   <>
Subject   st: RE: RE: Bessel
Date   Sat, 1 Oct 2005 17:43:21 +0100

Bobby Gutierrez needed some Bessel function 
for some purpose and wrote an undocumented helper
program. I can't remember which and can't find 
the code. 

I once wrote a rather specific Stata program for I_0, 
not what you specify here. 

1.5708 means _pi/2 here. 

Odds are you need to transliterate formulae
from Abramowitz and Stegun's handbook to Stata or Mata. 

> To be more specific, has anyone  made a Bessel of the 2nd 
> kind function in 
> Stata? An approximation is  sqrt(1.5708/x) * 
> sin(x-0.7854(2y+1)) for values 
> closer to the max values  and
> -[ (2^n)(n-1)! /pi ] * x^(-n) for values closer to 0. If 
> someone has a  
> better approximation, or the "exact" function in Stata, I'd 
> love to see  it.  

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