[R] -1.1 - 0.1 + 1.2 is NOT null! Why?

[William Dunlap]

It is for the same reason that if you must work with numbers
stored with 2 significant decimal digits 1-(1/3+1/3+1/3)
is 0.01 (== 10 ^ -2).

Double precision numbers, supported by your computer
hardware and used by R, are stored using 52 significant
binary digits and 2^-52 is about -2.220446e-16.

(By the way, in R zero and NULL are different things: the former
is numeric and the latter is not.)

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
> Behalf Of ollestrat
> Sent: Tuesday, July 10, 2012 1:17 PM
> To: r-help at r-project.org
> Subject: [R] -1.1 - 0.1 + 1.2 is NOT null! Why?
> 
> Hello,
> 
> I fear its a stupid question,..but here it is:
> 
> If I do this simple calculation with the R  console, I surprisingly do not
> get a zero. Why?
> 
>  -1.1-0.1+1.2
> [1] -2.220446e-16
> 
> 
> greetings, Ole
> 
> --
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> null-Why-tp4636053.html
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