R help - Oct 2008 - Simple addition and subtraction doesn't work??

I was working on a teaching example, but came across this weird result:
> q<-c(1.6,2.6, -3.4)
> q
[1]  1.6  2.6 -3.4
> sum(q)
[1] 0.8
> sum(q)- 0.8
[1] 2.22044605e-16

Why is the result not precisely zero?

Thanks!

AT

Depending on the class, you might have another teaching opportunity.

See R FAQ 7.31 and the document it points to.

Adrian Teo wrote:
> I was working on a teaching example, but came across this weird result:
> 
>> q<-c(1.6,2.6, -3.4)
>> q
> [1]  1.6  2.6 -3.4
>> sum(q)
> [1] 0.8
>> sum(q)- 0.8
> [1] 2.22044605e-16
> 
> Why is the result not precisely zero?
> 
> Thanks!
> 
> AT
> 
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