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Re: st: Stata cannot do math?


From   Ronan Conroy <rconroy@rcsi.ie>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Stata cannot do math?
Date   Thu, 19 May 2011 11:25:03 +0100

On 2011 Beal 19, at 01:20, Conor Hughes wrote:

> Hi,
> Stata can certainly do math, just not quite the same math you're used
> to.  This is an issue of floating point arithmetic.  For example,
> replace
> count a == 100.1
> in your code with
> count a == float(100.1)


I have a basic puzzle, which has just occurred to me: Stata cannot find any observations that satisfy the condition

count if a == 100.1

we know that Stata is representing the contents of the variable a as an inexact binary representation of 100.1, but why does it not represent the right hand argument in exactly the same way, causing the two to be equal? How does Stata represent the quantity 100.1 when it evaluates the expression a == 100.1?

Curious…


Ronán Conroy
rconroy@rcsi.ie
Associate Professor
Division of Population Health Sciences
Royal College of Surgeons in Ireland
Beaux Lane House
Dublin 2


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