That (and simpler, sprintf()) merely tell you about your OS's sprintf
function. That is not required to accurately give a decimal
representation of more than DECIMAL_DIG digits, and certainly not 50.
The help for formatC does warn you about this.
On my F8 system DECIMAL_DIG is mentioned in math.h but not defined there.
(It is defined in the compiler, AFAICS -- SunStudio has it as 21, and gcc
computes __DECIMAL_DIG__ also as 21.) The C99 standard says that it
should be at least 10 and that 17 is appropriate for IEC60559 arithmetic.
On Wed, 4 Jun 2008, Karl Ove Hufthammer wrote:
Duncan Murdoch:
The number 0.12345 is not exactly representable, but (I think) it is
represented by something slightly closer to 0.1235 than to 0.1234.
I like using formatC for checking such things. On my (Linux) system, I get:
$ formatC(.12345,digits=50)
[1] "0.12345000000000000417443857259058859199285507202148"
So it looks as though Windows gets it right.
--
Karl Ove Hufthammer
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
--
Brian D. Ripley, [EMAIL PROTECTED]
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
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
