| 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.