gompertzd: The derivative of the Gompertz function
Description
'gompertzd' provides a way of specifying the derivative of the Gompertz function
as a dose-response model.
Usage
gompertzd(fixed = c(NA, NA), names = c("a", "b"))
Arguments
fixed
numeric vector. Specifies which parameters are fixed and at what value they are fixed.
NAs for parameter that are not fixed.
names
a vector of character strings giving the names of the parameters (should not contain ":").
The default is (notice the order): a, b.
Value
The value returned is a list containing the model function, the self starter function
and the parameter names.
Details
The derivative of the Gompertz function is defined as
$$f(x) = a \exp(bx-a/b(exp(bx)-1))$$
For $a>0$ and $b$ not 0, the function is decreasing, equaling $a$ at $x=0$
and approaching 0 at plus infinity.