I think he means something like packages Rmpfr and gmp provide.
However, careful numerical analysis (and working with x-1 or log(x)
for numbers very near one) means that such packages are rarely
necessary (although they can be very convenient).
It all depends on the calculations: vague questions necessitate vague
answers.
On Fri, 30 Oct 2009, Ista Zahn wrote:
Hi Greg,
Others on this list are much more knowledgeable than I am, and I'm
sure they will correct me if I'm wrong.
My understanding is that R uses double precision (see
http://en.wikipedia.org/wiki/Double_precision_floating-point_format),
which has the following implication:
x <- c(1,2,3)/10^308
x*10^308
[1] 1 2 3
x <- c(1,2,3)/10^309
x*10^309
[1] NaN NaN NaN
among others. See
RSiteSearch("floating point")
for other additional implications. I think you're out of luck it you
need to work with values smaller than 1*10^308.
-Ista
On Fri, Oct 30, 2009 at 5:04 PM, Greg Michaelson <gmichael...@me.com> wrote:
I would like to increase the precision/accuracy of R. That is, I'm dealing
with numbers exceedingly close to 1, and I would like to increase the number
of significant digits used in computation. In matlab, you can use vpa() to
accomplish this. I'm wondering if there's an equivalent or a workaround in
R.
Greg
--
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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