reciprocal {VGAM} | R Documentation |
Computes the reciprocal transformation, including its inverse and the first two derivatives.
reciprocal(theta, bvalue = NULL, inverse = FALSE, deriv = 0, short = TRUE, tag = FALSE) negreciprocal(theta, bvalue = NULL, inverse = FALSE, deriv = 0, short = TRUE, tag = FALSE)
theta |
Numeric or character. See below for further details. |
bvalue |
See |
inverse, deriv, short, tag |
Details at |
The reciprocal
link function is a special case of the power link
function. Numerical values of theta
close to 0 result in
Inf
, -Inf
, NA
or NaN
.
The negreciprocal
link function computes the negative reciprocal,
i.e., -1/theta.
For reciprocal
:
for deriv = 0
, the reciprocal of theta
, i.e.,
1/theta
when inverse = FALSE
,
and if inverse = TRUE
then
1/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.
Numerical instability may occur when theta
is
close to 0.
Thomas W. Yee
McCullagh, P. and Nelder, J. A. (1989) Generalized Linear Models, 2nd ed. London: Chapman & Hall.
reciprocal(1:5) reciprocal(1:5, inverse = TRUE, deriv = 2) negreciprocal(1:5) negreciprocal(1:5, inverse = TRUE, deriv = 2) x <- (-3):3 reciprocal(x) # Has Inf reciprocal(x, bvalue = .Machine$double.eps) # Has no Inf