On 11-10-09 4:00 AM, (Ted Harding) wrote:
On 09-Oct-11 00:46:58, Carl Witthoft wrote:
On 10/8/11 6:11 PM, (Ted Harding) wrote:
Carl Witthoft's serendipitous discovery is a nice example
of how secrets can be guessed by wondering "what if ... ?".
So probably you don;t need to tell the secrets.
Taking the "negative digits" to their logical extreme:
round(654.321,2)
# [1] 654.32
round(654.321,1)
# [1] 654.3
round(654.321,0)
# [1] 654
round(654.321,-1)
# [1] 650
round(654.321,-2)
# [1] 700
round(654.321,-3)
# [1] 1000
round(654.321,-4)
# [1] 0
which is what you'd logically expect (but is it what you
would intuitively expect?).
Oh, oh, somebody's going all metaphysical on us.
Nor should one forget the rounding rules (not OS-dependent
in this case, I think ... ?):
round(5000,-4)
# [1] 0
round(15000,-4)
# [1] 20000
The intention is that those are not OS dependent, but since they rely on
exact representations, there could be differences: not all platforms
support the "extended real" 80 bit intermediate representations. (If
you were rounding to 0 d.p., they should all agree on a "round to even"
rule. Rounding to -4 d.p. involves dividing by 10^4, and that could
lead to errors.)
Duncan Murdoch
______________________________________________
[email protected] 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.
