[1] "5.9999999999999991"
format(10^5.9999999999999991,digits=18)
[1] "999999.9999999979"
Version:
platform = sparc-sun-solaris2.7
arch = sparc
os = solaris2.7
system = sparc, solaris2.7
status =
major = 1
minor = 3.0
year = 2001
month = 06
day = 22
language = R
Search Path:
.GlobalEnv, package:RODBC, package:MASS, package:prlib, package:pllib,
package:mathlib, package:mva, package:strlib, package:chlib, Autoloads,
package:base
Dr.sc.math.Christian W. Hoffmann
Mathematics and Statistical Computing
Landscape Modeling and Web Applications
Swiss Federal Research Institute WSL
Zuercherstrasse 111
CH-8903 Birmensdorf, Switzerland
phone: ++41-1-739 22 77 fax: ++41-1-739 22 15
e-mail: christian.hoffmann_at_wsl.ch__prevent_spamming
www: http://www.wsl.ch/staff/christian.hoffmann/
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"ChHo" == christian hoffmann <christian.hoffmann@wsl.ch> writes:
ChHo> format((1000000*(1+.Machine$double.eps)),digits=18)
ChHo> [1] "1000000.0000000002"
>> .Machine$double.rounding
ChHo> [1] 5
ChHo> format(log10(1000000*(1+.Machine$double.eps)),digits=18)
ChHo> [1] "5.9999999999999991" # MUST be > 6 !!!???
no.
you assume that every arithmetic operation is correct to the last
bit, which is too much. Note that you have two conversions
decimal <-> binary, and log10(x) internally really maps to log(x)/log(10)
(where log(10) is stored as constant).
ChHo> format((1000000*(1-.Machine$double.eps)),digits=18)
ChHo> [1] " 999999.9999999998"
>> format(log10(1000000*(1-.Machine$double.eps)),digits=18)
ChHo> [1] "5.9999999999999991"
ChHo> format(10^5.9999999999999991,digits=18)
ChHo> [1] "999999.9999999979"
You have to expect more than one bit difference..
Definitely no bug.
Martin Maechler <maechler@stat.math.ethz.ch> http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum LEO D10 Leonhardstr. 27
ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND
phone: x-41-1-632-3408 fax: ...-1228 <><
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