loge {VGAM} | R Documentation |
Computes the log transformation, including its inverse and the first two derivatives.
loge(theta, earg = list(), inverse = FALSE, deriv = 0, short = TRUE, tag = FALSE) nloge(theta, earg = list(), inverse = FALSE, deriv = 0, short = TRUE, tag = FALSE)
theta |
Numeric or character.
See below for further details.
|
earg |
Optional list. Extra argument for passing in additional information.
Values of theta which are less than or equal to 0 can be
replaced by the bvalue component of the list earg
before computing the link function value.
The component name bvalue stands for ``boundary value''.
See Links for general information about earg .
|
inverse |
Logical. If TRUE the inverse function is computed. |
deriv |
Order of the derivative. Integer with value 0, 1 or 2. |
short |
Used for labelling the blurb slot of a
vglmff-class object.
|
tag |
Used for labelling the linear/additive predictor in the
initialize slot of a vglmff-class object.
Contains a little more information if TRUE .
|
The log link function is very commonly used for parameters that
are positive.
Numerical values of theta
close to 0 or out of range
result in
Inf
, -Inf
, NA
or NaN
.
The arguments short
and tag
are used only if
theta
is character.
The function loge
computes
log(theta) whereas nloge
computes
-log(theta)=log(1/theta).
The following concerns loge
.
For deriv = 0
, the log of theta
, i.e., log(theta)
when inverse = FALSE
, and if inverse = TRUE
then
exp(theta)
.
For deriv = 1
, then the function returns
d theta
/ d eta
as a function of theta
if inverse = FALSE
,
else if inverse = TRUE
then it returns the reciprocal.
Here, all logarithms are natural logarithms, i.e., to base e.
This function is called loge
to avoid conflict with the
log
function.
Numerical instability may occur when theta
is close to 0 unless
earg
is used.
Thomas W. Yee
McCullagh, P. and Nelder, J. A. (1989) Generalized Linear Models, 2nd ed. London: Chapman & Hall.
Links
,
logit
,
logc
,
loglog
,
log
,
logoff
.
## Not run: loge(seq(-0.2, 0.5, by=0.1)) loge(seq(-0.2, 0.5, by=0.1), earg=list(bvalue= .Machine$double.xmin)) nloge(seq(-0.2, 0.5, by=0.1)) nloge(seq(-0.2, 0.5, by=0.1), earg=list(bvalue= .Machine$double.xmin)) ## End(Not run)