Self-Starting nls logistic model

Computes the logistic function

SSlogis2(input,alpha,beta,gamma)

Arguments

input	a numeric vector of values at which to evaluate the model.
alpha	estimated model parameter
beta	estimated model parameter
gamma	estimated model parameter

Value

a numeric vector of the same length as input. It is the value of the expression alpha/(1+beta*exp(-gamma*x)).

Note

This is primarily intended for use in formulae given to the nls function or similar functions for example mle2.

References

Goryl A., Jedrzejczyk Z., Kukula K. (Eds.), Osiewalski J., Walkosz A. (2004) "Wprowadzenie do ekonometrii w przykladach i zadaniach", Wydawnictwo Naukowe PWN, Warszawa.

Borkowski B., Dudek H., Szczesny W. (2004) "Ekonometria. Wybrane zagadnienia" , Wydawnictwo Naukowe PWN, Warszawa.

See also

SSlogis, selfStart, getInitial

Examples

set.seed(46)
x <- 1:15
y <- 1/(1+exp(7-1.5*x))+rnorm(15,0,0.1)
model <- nls(y~SSlogis2(x,alpha,beta,gamma))