On 1/11/2010 10:37 AM, Martin Maechler wrote:
Magnus Torfason<zulutime....@gmail.com wrote:
Of course there is still the problem that:
> 1+1 == sqrt(2)*sqrt(2)
[1] FALSE
and gmp will not solve this . I don't know if there is an R-package for
arbitrary-precision reals floating around, but probably not.
Yes, there's package 'Rmpfr' for arbitrary precision
floating-point, written and maintained by me.
However, that does *still* not allow the equivalent
of
1+1 == sqrt(2)*sqrt(2)
because that would need *infinite* precision not just arbitrary
precision, or then *symbolic* computation, as I assume the following does
Very true! I got my jargon mixed up. I was in fact referring to symbolic
computation when i wrote that. In the meantime I had found the Rmpfr
package, which installed from CRAN without a hitch on my Windows Vista
computer. Nevertheless, I look forward to receiving the latest update
once it propagates through CRAN.
I think the gmp and Rmpfr packages need more airtime in R circles, since
issues of precision come up all the time and they provide a very
straight-forward way of addressing the issue. Perhaps they should be
added to FAQ 7.31?
Best,
Magnus
______________________________________________
R-help@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.
