Impressive. Never ceases to amaze me what computers can do these days. ;-)
It's even more impressive given that we have
static double logbase(double x, double base)
{
#ifdef HAVE_LOG10
if(base == 10) return x > 0 ? log10(x) : x < 0 ? R_NaN : R_NegInf;
#endif
#ifdef HAVE_LOG2
if(base == 2) return x > 0 ? log2(x) : x < 0 ? R_NaN : R_NegInf;
#endif
return R_log(x) / R_log(base);
}
which, except possibly for base-10 and base-2, would seem to be quite hard to
convince to return anything other than 1 if x == base....
-pd
On 02 Sep 2014, at 03:27 , Ben Bolker <bbol...@gmail.com> wrote:
> log(8, base=8L)-1
> log(8, base=8)-1
> logvals <- setNames(log(2:25,base=2:25)-1,2:25)
> logvals[logvals!=0] ## 5,8,14,18,19,25 all == .Machine$double.eps/2
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
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