[R] Problem with long number (from character to numeric class)

[David Winsemius]

On Feb 9, 2011, at 7:15 AM, PtitBleu wrote:

>
> Hello,
>
> I have a text file with one column containing long number but stored  
> as
> string.
> I download the file with read.table (and colClass) and the first row  
> of this
> column is :
>
> "095842087016731010"
>
> As I need to make some calculations with these numbers, I tried to  
> convert
> them using as.numeric.
> But then I get
> as.numeric("095842087016731010")
> 95842087016731008

Your number is many powers of ten above the maximum possible integer  
value 2*10^9. So you are seeing the floating point number that  
resulted from coercion, and R does not have arbitrary precision  
arithmetic in its base repertoire.

> I understand the disappearing of the first 0 but I don't understand  
> the
> substitution of the last 0 by 8.
>
> Is there a way to avoid that ?

There is a package that handles bignums, Brobdingnag.
. And there is interfaces to the symbolic algebra system, Yacas.  
But.... Do you really need arbitrary precision?


> Thanks in advance,
> Ptit Bleu.
> -- 


David Winsemius, MD
West Hartford, CT