[R] numeric equality

[Bernardo Rangel Tura]

On Wed, 2009-03-18 at 11:58 -0400, Yu, Changhong wrote:
> Dear all,
> 
>  
> 
> I am totally confused by the following R output, but don't have a clue
> for it.
> 
>  
> 
> > a <- 1 - 0.2
> 
> > a == 0.8
> 
> [1] TRUE
> 
> > a <- 1 - 0.8
> 
> > a == 0.2
> 
> [1] FALSE

Hi Yu,

First of all read FAQ 7.31 (Why doesn't R think these numbers are
equal?)

Second, in this case, use all.equal

a <- 1 - 0.8

a == 0.2
[1] FALSE

all.equal(a,0.2)
[1] TRUE

-- 
Bernardo Rangel Tura, M.D,MPH,Ph.D
National Institute of Cardiology
Brazil