Message-ID: <8760D6386F7F784693F05256139A1FFB70F87A@EXCHF3.lse.ac.uk>
Date: 2007-12-21T19:52:29Z
From: C.Rosa at lse.ac.uk
Subject: Numerical precision problem
Dear All,
I have a numerical problem:
R, as other statistical software, can tell the difference between very small numbers and 0, while apparently cannot distinguish a number close to 1 and 1. In the example below, is it possible to instruct R to recognize that q is different from 1?
> p=.00000000000000000000000000000001
> p==0
[1] FALSE
> q=.99999999999999999999999999999
> q==1
[1] TRUE
Interestingly,
> (1-p)==1
[1] TRUE
The main problem I have is that I need to evaluate the inverse of the normal Cumulative Distribution Function near 1 (but not exactly 1) and the PC cannot recognize it.
Thank you very much for your help!
Carlo
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