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Re: st: Format problem?


From   Neil Shephard <nshephard@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Format problem?
Date   Sun, 29 Jan 2006 09:15:20 +0800

On 1/29/06, Andrzej Niemierko <aniemierko@partners.org> wrote:
> Could someone please explain to me the following strange behaviour? When I
> generate a new variable:
> gen x1=3366161 and then:
> gen x2=10*x1
> the number that I get for x2 is 33661608 (not the correct number 33661610).
> When the initial x1 number is 3366162 the x2 is correct, that is 33661620.
> Any help?
> Sorry if this is double post (from a different account).

Its not a problem specific to Stata, but is more general to copmuters
and boils down to the fact that computers work in binary and there are
some numbers that you can't represent accurately in binary.

For a brief overview in Stata see -man datatypes-, but for more
information see some the archives, heres a start (searched using the
term "precision")...

http://www.stata.com/slsearch.cgi?q=precision&t=statalist

HTH's

Neil
--
Email - nshephard@gmail.com
Website - http://slack.ser.man.ac.uk/
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