Evaluate at a particular set of parameters the log-Gompertz function.
loggompertz_fn(x, theta)Numeric vector of the same length of x with the values of the
log-logistic function.
numeric vector at which the function is to be evaluated.
numeric vector with the four parameters in the form
c(alpha, delta, eta, phi).
The log-Gompertz function f(x; theta) is defined here as
f(x; theta) = alpha + delta exp(-(phi / x)^eta)
where x >= 0, theta = c(alpha, delta, eta, phi), eta > 0, and
phi > 0. By convention we set
f(0; theta) = lim_{x -> 0} f(x; theta) = alpha.