exp(x) log(x) logb(x, base=exp(1)) log10(x) log2(x) sqrt(x) log1p(x) expm1(x)
NA
s) are allowed.
log1p
and
expm1
do not
accept complex inputs.
log
computes natural logs.
log1p(x)
computes
log(1+x)
but avoids the loss of precision in computing
1+x
when
x
is close to 0.
expm1(x)
computes
exp(x)-1
but is more accurate than the naive expression when
x
is close to 0.
This function will be used as the default method for classes that do not inherit a specific method for the function or for the Math group of functions. The result will retain the class and the attributes. If this behavior is not appropriate, the designer of the class should provide a method for the function or for the Math group
Missing in input means output missing.
Numeric arguments must be non-negative for
log
,
logb
,
log10
,
log2
,
and
sqrt
,
otherwise
NA is returned and a warning message is generated;
coerce the numbers to complex to avoid this.
The functions
exp
,
log
,
expm1
, and
log1p
are members
of the
Math
group of generic functions.
Because members of this group have only one argument,
the
logb
function replaces
the old
log
function
when you need to specify a base for the logarithm.
log10
and
log2
call
logb
with base equal to 10 and 2, respectively.
See section 5.1.5 of Becker, Chambers and Wilks for details on domains and branch cuts in the case of complex arguments.
Becker, R.A., Chambers, J.M., and Wilks, A.R. (1988). The New S Language Wadsworth and Brooks/Cole, Pacific Grove, CA.
log2(64) # base 2 logarithms logb(100, 10) == log10(100) # log10 computes the common logarithm log(-3) # returns NA log(as.complex(-3)) # equals log(3) plus pi times i arc <- seq(0, pi/2, len=50) exp((1i) * arc) # part of the unit circle in the complex plane sqrt(2) log1p(1e-10) # slightly less than 1e-10 log1p(1e-20) # c. 1e-20, not the 0 that log(1+1e-20) gives expm1(1e-20) # c. 1e-20, not the 0 that exp(1e-20)-1 gives