[R] Problem about zero

[Joshua Wiley]

Hello Yen,

You may find ?zapsmall helpful.  If your algorithm expects 1-sum(x) to
have a lower bound of zero, then also simply setting a cutoff point
seems reasonable.

Josh

On Tue, Jun 15, 2010 at 3:00 PM, Yen Lee <b88207001 at ntu.edu.tw> 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.
>
>
>
> Thank you so much.
>
>
>
> Yen
>
>
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>
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-- 
Joshua Wiley
Ph.D. Student
Health Psychology
University of California, Los Angeles