loglogistic2_fn {drda}  R Documentation 
2parameter loglogistic function
Description
Evaluate at a particular set of parameters the 2parameter loglogistic 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 2parameter loglogistic 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
loglogistic function.