R help - Feb 2010 - Help for numbers close to 1 in R

Hi all.

I have a problem with adding 1 and very small numbers

ex:
>p=1e-49
>1+p
[1] 1

My problem comes from some values of x for the value:
    1-exp(-sum((x-1/sqrt(3))^2))
the return values are always equivalent.

Please help
Thanks
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On Sat, Feb 13, 2010 at 2:17 PM, cjmr <cjregunay at gmail.com>
wrote:
>>p=1e-49
>>1+p
> [1] 1
>
Try this:
> source("http://r-bc.googlecode.com/svn/trunk/R/bc.R")
> p <- bc(1e-49)
> p
[1]
".0000000000000000000000000000000000000000000000001"
> 1+p
[1] "1.0000000000000000000000000000000000000000000000001"

You might want to check this [1] and search the archives for
"precision".
Liviu

[1] http://code.google.com/p/r-bc/

> My problem comes from some values of x for the value:
> ? ?1-exp(-sum((x-1/sqrt(3))^2))
> the return values are always equivalent.
>
> Please help
> Thanks
> --
> View this message in context:
http://n4.nabble.com/Help-for-numbers-close-to-1-in-R-tp1554416p1554416.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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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On Sat, Feb 13, 2010 at 9:17 AM, cjmr <cjregunay at gmail.com>
wrote:
>
> Hi all.
>
> I have a problem with adding 1 and very small numbers
>
> ex:
>>p=1e-49
>>1+p
> [1] 1
>
> My problem comes from some values of x for the value:
> ? ?1-exp(-sum((x-1/sqrt(3))^2))
> the return values are always equivalent.
>
> Please help
> Thanks
> --
> View this message in context:
http://n4.nabble.com/Help-for-numbers-close-to-1-in-R-tp1554416p1554416.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.
>