[R] log10(), floor() combo issue?
Peter Dalgaard BSA
p.dalgaard at biostat.ku.dk
Mon Oct 14 12:31:02 CEST 2002
"E.L. Willighagen" <egonw at sci.kun.nl> writes:
> The reason is the combination of floor() and log10():
> log10(1000) = 3
> ok, but:
> floor(log10(1000)) = 2
> ? Ok, I can live with some floating point inaccuracy, but this seems
> at least a bit strange, and to me troublesome as it makes the bindec()
> method fail...
Well, the reason is of course that
Having log10 exact for integer powers of 10 is apparently too much to
ask from a binary computer, although it might in principle be possible
(but I believe log10(x) is computed as log(x)/log(10)). For negative
powers it really is impossible.
> I've also tried to force the output of log10(1000) into integer format
> However, with the same disappointing results...
(as.integer() truncates, so floor() is superfluous)
The only way out is to add "fuzz" as in
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch
More information about the R-help