SSGompertz {statforbiology} | R Documentation |
Gompertz equations
Description
These functions provide the Gompertz equations with 4 (G4.fun), 3 (G3.fun)
and 2 (G2.fun) parameters with self-starter for the nls
function (NLS.G4, NLS.G3 and NLS.G2).
Usage
G4.fun(predictor, b, c, d, e)
G3.fun(predictor, b, d, e)
G2.fun(predictor, b, e)
NLS.G4(predictor, b, c, d, e)
NLS.G3(predictor, b, d, e)
NLS.G2(predictor, b, e)
Arguments
predictor |
a numeric vector of values at which to evaluate the model |
b |
model parameter (slope at inflection point) |
c |
model parameter (lower asymptote) |
d |
model parameter (higher asymptote) |
e |
model parameter (abscissa at inflection point) |
Details
The Gompertz equation is parameterised as:
f(x) = c + (d - c) \, \exp \left[-exp(-b (x - e))\right]
It is a sygmoidally shaped curve and it is asymmetric about its inflection point. For the 3- and 2-parameter model c is equal to 0, while for the 2-parameter model d is equal to 1.
Value
All these functions return a numeric value.
Author(s)
Andrea Onofri
Examples
data(beetGrowth)
mod3 <- nls(weightInf ~ NLS.G3(DAE, b, c, d), data = beetGrowth)
summary(mod3)
plot(mod3)
[Package statforbiology version 0.9.9 Index]