Frank Mattes <f.mattes at ucl.ac.uk> writes:
> Dear R users,
>
> according the help(log), the function
> log2(x) should give the natural logarithm of x.
>
> I expect in case of x=2 to to get 0.6931, however, R gives me 1 as a
result.
>
> Similar, logb(2,2) gives 1 again.
>
> I'm wondering if I have missed something ?
>
I think you are looking at the help page wrong:
Description:
'log' computes natural logarithms, 'log10' computes common
(i.e.,
base 10) logarithms, and 'log2' computes binary (i.e., base 2)
logarithms. The general form 'logb(x, base)' computes logarithms
with base 'base' ('log10' and 'log2' are only
special cases).
'log1p(x)' computes log(1+x) accurately also for |x| << 1
(and
less accurately when x is approximately -1).
'exp' computes the exponential function.
'expm1(x)' computes exp(x) - 1 accurately also for |x| << 1.
log() is what you want.
--
rossini at u.washington.edu http://www.analytics.washington.edu/
Biomedical and Health Informatics University of Washington
Biostatistics, SCHARP/HVTN Fred Hutchinson Cancer Research Center
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