[R] big numbers
Roger D. Peng
rdpeng at gmail.com
Tue Aug 22 15:58:37 CEST 2006
The 'gmp' package may be of use here, but I'm not sure.
-roger
Robin Hankin wrote:
> Hi
>
> Can I get R to handle really big numbers? I am not interested
> in more than (say) 10 sig figs, but I would like to deal with numbers
> up to, say, 10^10000.
>
> If
>
> a <- 10^10000
> b <- pi* a
>
> I would like "a+b" to return 3.1415926e10000.
>
>
> Toy example, illustrating why I can't deal with log(a) and log(b),
> follows.
>
>
>
> f <- function(a,n=100){
> out <- rep(0,n)
> out[1] <- a
> for(i in 2:n){
> out[i] <- sum(exp(out[1:i])) + rexp(1)
> }
> return(log(out))
> }
>
>
> then f(1,10) has infinities in it, even though the values should be
> moderate size.
>
> What are my options here?
>
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
> tel 023-8059-7743
>
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>
--
Roger D. Peng | http://www.biostat.jhsph.edu/~rpeng/
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