Asymptotic Regression Model

The base function for the asymptotic regression model, providing the mean function and self starter for a three-parameter model.

Usage

arandaordaz(fixed = c(NA, NA, NA), names = c("a", "b", "c"), fctName, fctText)

fixed: numeric vector. Specifies which parameters are fixed and at what value they are fixed. Use NA for parameters that are not fixed. Must be of length 3.
names: character vector of length 3 giving the names of the parameters (should not contain ":").
fctName: optional character string used internally by convenience functions. Defaults to "arandaordaz" if not provided.
fctText: optional character string used internally by convenience functions. Defaults to "Asymptotic regression" if not provided.

A list of class drcMean with the following components:

fct: The mean function taking arguments dose and parm.
ssfct: Self-starter function for generating initial parameter estimates from data.
names: Character vector of non-fixed parameter names.
deriv1: Reserved first derivative slot (currently NULL).
deriv2: Reserved second derivative slot (currently NULL).
derivx: Reserved derivative-with-respect-to-x slot (currently NULL).
edfct: Function for calculating effective dose (ED) values and their derivatives.
inversion: Inverse mean function for back-calculating dose from response.
name: Character string identifying the model function name.
text: Character string with a human-readable model description.
noParm: Integer giving the number of non-fixed parameters.

The asymptotic regression model is a three-parameter model with mean function:

$$f(x) = c + (d-c)(1-\exp(-x/e))$$

The parameter $c$ is the lower limit (at $x=0$), $d$ is the upper limit, and $e>0$ determines the steepness of the increase.

Christian Ritz, Hannes Reinwald