| log {base} | R Documentation |
Logarithms and Exponentials
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| \ll 1 (and less accurately when x \approx
-1).
exp computes the exponential function.
expm1(x) computes \exp(x) - 1 accurately also for
|x| \ll 1.
Usage
log(x, base = exp(1))
logb(x, base = exp(1))
log10(x)
log2(x)
exp(x)
expm1(x)
log1p(x)
Arguments
x |
a numeric or complex vector. |
base |
positive number. The base with respect to which
logarithms are computed. Defaults to |
Details
exp and log are generic functions: methods can be defined
for them individually or via the Math group generic.
Value
A vector of the same length as x containing the transformed
values. log(0) gives -Inf (when available).
Note
log and logb are the same thing in R, but logb
is preferred if base is specified, for S-PLUS compatibility.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
The New S Language.
Wadsworth \& Brooks/Cole.
(for log, \log10 and exp.)
Chambers, J. M. (1998)
Programming with Data. A Guide to the S Language.
Springer. (for logb.)
See Also
Trig,
sqrt,
Arithmetic.
Examples
log(exp(3))
log10(1e7)# = 7
x <- 10^-(1+2*1:9)
cbind(x, log(1+x), log1p(x), exp(x)-1, expm1(x))