Re: [R] Problem about zero

From: Jorge Ivan Velez <jorgeivanvelez_at_gmail.com>
Date: Tue, 15 Jun 2010 18:44:38 -0400

Same for me on Mac OS X:

> x <- c(0.1819711,0.4811463,0.1935151,0.1433675)
> 1-sum(x)
[1] 0
> version$version.string

[1] "R version 2.11.1 Patched (2010-05-31 r52180)"

Regards,
Jorge

On Tue, Jun 15, 2010 at 6:40 PM, Gabor Grothendieck <> wrote:

> On Tue, Jun 15, 2010 at 6:00 PM, Yen Lee <> wrote:
> > Hello, everyone,
> >
> > There's a problem about zero in R and I really need your help.
> >
> >
> >
> > I have a vector shown as x=c(0.1819711,0.4811463,0.1935151,0.1433675),
> >
> > The sum of this vector is shown as 1 in R, but when I type 1-sum(x), the
> > value is not zero, but -2.220446e-16.
> >
> > I can accept that this value is quite small and could be seen as zero,
> but
> > there would be a problem when it's not really zero but a negative value
> in
> > my algorithm.
> >
> >
> >
> > Therefore I would like to know that how could it be avoid.
> >
> > One way I think is to define the value 1-sum(x) as zero when it is
> smaller
> > than a particular value, but the particular value is not be set yet.
> >
> > I would like to know more about the definition of the shown zero in R.
> >
>
> As others have pointed out please read the R FAQ.
>
> Actually on my machine: Windows Vista running C2D BLAS, "R version
> 2.11.1 Patched (2010-05-31 r52167)"
> I do get zero:
>
> > x <- c(0.1819711,0.4811463,0.1935151,0.1433675)
> > 1-sum(x)
> [1] 0
>
> Also check out sum.exact in the caTools package.
>
> ______________________________________________
> R-help_at_r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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