| loglogistic2_fn {drda} | R Documentation |
2-parameter log-logistic function
Description
Evaluate at a particular set of parameters the 2-parameter log-logistic function.
Usage
loglogistic2_fn(x, theta)
Arguments
x |
numeric vector at which the function is to be evaluated. |
theta |
numeric vector with the four parameters in the form
|
Details
The 2-parameter log-logistic function f(x; theta) is defined here as
g(x; theta) = x^eta / (x^eta + phi^eta)
f(x; theta) = alpha + delta g(x; theta)
where x >= 0, theta = c(alpha, delta, eta, phi), eta > 0, and
phi > 0. Only eta and phi are free to vary (therefore the name) while
vector c(alpha, delta) is constrained to be either c(0, 1) (monotonically
increasing curve) or c(1, -1) (monotonically decreasing curve).
This function allows values other than 0, 1, -1 for alpha and delta but
will coerce them to their proper constraints.
Value
Numeric vector of the same length of x with the values of the
log-logistic function.