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(lowerc = c(-Inf, -Inf), upperc = c(Inf, Inf),
fixed = c(NA, NA), names = c("a", "b"))Arguments
lowerc
numeric vector. The lower bound on parameters. Default is minus infinity.
upperc
numeric vector. The upper bound on parameters. Default is plus infinity.
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 non-linear 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.