gompertz_fn {drda}  R Documentation 
Gompertz function
Description
Evaluate at a particular set of parameters the Gompertz function.
Usage
gompertz_fn(x, theta)
Arguments
x 
numeric vector at which the Gompertz function is to be evaluated. 
theta 
numeric vector with the four parameters in the form

Details
The Gompertz function f(x; theta)
is defined here as
g(x; theta) = exp(exp(eta * (x  phi)))
f(x; theta) = alpha + delta g(x; theta)
where theta = c(alpha, delta, eta, phi)
, alpha
is the value of the
function when x > Inf
, delta
is the (signed) height of the curve,
eta > 0
is the steepness of the curve or growth rate, and phi
is related
with the value of function at x = 0
.
When delta < 0
the curve is monotonically decreasing while it is
monotonically increasing for delta > 0
.
Value
Numeric vector of the same length of x
with the values of the
Gompertz function.