The derivative of the Gompertz function

'gompertzd' provides a way of specifying the derivative of the Gompertz function as a dose-response model.

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.

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.

The value returned is a list containing the model function, the self starter function and the parameter names.

This function is for use with the function drm.