VGAM (version 1.1-2)

explink: Exponential Link Function

Description

Computes the exponential transformation, including its inverse and the first two derivatives.

Usage

explink(theta, bvalue = NULL, inverse = FALSE, deriv = 0, short = TRUE, tag = FALSE)

Arguments

theta

Numeric or character. See below for further details.

bvalue

See clogloglink.

inverse, deriv, short, tag

Details at Links.

Value

For explink with deriv = 0, the exponential of theta, i.e., exp(theta) when inverse = FALSE. And if inverse = TRUE then log(theta); if theta is not positive then it will return NaN.

For deriv = 1, then the function returns d eta / d theta 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.

Details

The exponential link function is potentially suitable for parameters that are positive. Numerical values of theta close to negative or positive infinity may result in 0, Inf, -Inf, NA or NaN.

See Also

Links, loglink, rcim, Qvar, uninormal.

Examples

# NOT RUN {
theta <- rnorm(30)
explink(theta)
max(abs(explink(explink(theta), inverse = TRUE) - theta))  # Should be 0
# }