Gompertz dose-response or growth curve model

Provides a very general way of specifying the mean function of the decreasing or increasing Gompertz dose-response or growth curve models.

Usage

gompertz(
  fixed = c(NA, NA, NA, NA),
  names = c("b", "c", "d", "e"),
  method = c("1", "2", "3", "4"),
  ssfct = NULL,
  fctName,
  fctText
)

fixed: numeric vector. Specifies which parameters are fixed and at what value they are fixed. NAs for parameters that are not fixed.
names: vector of character strings giving the names of the parameters (should not contain ":"). The order of the parameters is: b, c, d, e.
method: character string indicating the self starter function to use.
ssfct: a self starter function to be used.
fctName: optional character string used internally by convenience functions.
fctText: optional character string used internally by convenience functions.

A list containing the non-linear function, the self starter function and the parameter names.

The Gompertz model is given by the mean function $$f(x) = c + (d-c)(\exp(-\exp(b(x-e))))$$

If $b<0$ the mean function is increasing; it is decreasing for $b>0$.

Seber, G. A. F. and Wild, C. J. (1989) Nonlinear Regression, New York: Wiley & Sons (p. 331).

Christian Ritz