drc (version 2.0-1)

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.