| log {base} | R Documentation |
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.
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(x, base = exp(1)) logb(x, base = exp(1)) log10(x) log2(x) log1p(x) exp(x) expm1(x)
x |
a numeric or complex vector. |
base |
a positive or complex number: the base with respect to which
logarithms are computed. Defaults to e=exp(1). |
exp, expm1, log and log1p are generic
functions: methods can be defined for them individually or via the
Math group generic.
log10 and log2 are only convenience wrappers, but logs
to bases 10 and 2 (whether computed via log or the wrappers)
will be computed more efficiently and accurately where supported by the OS.
logb is a wrapper for log for compatibility with S. If
(S3 or S4) methods are set for log they will be dispatched.
Do not set S4 methods on logb itself.
A vector of the same length as x containing the transformed
values. log(0) gives -Inf (when available).
exp is S4 generic and a member of the
Math group generic.
log and logb are the same thing in R, but logb
is preferred if base is specified, for S-PLUS compatibility.
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.)
Trig,
sqrt,
Arithmetic.
log(exp(3)) log10(1e7)# = 7 x <- 10^-(1+2*1:9) cbind(x, log(1+x), log1p(x), exp(x)-1, expm1(x))