betareg.control: Control Parameters for Beta Regression

Description

Various parameters that control fitting of beta regression models using betareg.

Usage

betareg.control(phi = TRUE, method = "BFGS", maxit = 5000,
  hessian = FALSE, trace = FALSE, start = NULL, ...)

Arguments

phi

logical indicating whether the precision/dispersion parameter phi should be treated as a full model parameter (TRUE, default) or as a nuisance parameter.

method

characters string specifying the method argument passed to optim.

maxit

integer specifying the maxit argument (maximal number of iterations) passed to optim.

trace

logical or integer controlling whether tracing information on the progress of the optimization should be produced (passed to optim).

hessian

logical. Should the numerical Hessian matrix from the optim output be used for estimation of the covariance matrix? If FALSE (the default), the analytical solution is employed.

start

an optional vector with starting values for all parameters (including phi).

...

arguments passed to optim.

Value

A list with the arguments specified.

Details

All parameters in betareg are estimated by maximum likelihood using optim with control options set in betareg.control. Most arguments are passed on directly to optim, only start controls how optim is called.

Starting values can be supplied via start or estimated by lm.wfit, using the link-transformed response. Covariances are derived analytically (if hessian = FALSE, the default) or numerically using the Hessian matrix returned by optim. The main parameters of interest are the coefficients in the linear predictor of the model and the additional precision/dispersion parameter phi which can either be treated as a full model parameter (default) or as a nuisance parameter. In the latter case the estimation does not change, only the reported information in output from print, summary, or coef (among others) will be different. See also examples.

Examples

Run this code

data("GasolineYield", package = "betareg")

## regression with phi as full model parameter
gy1 <- betareg(yield ~ batch + temp, data = GasolineYield)
gy1

## regression with phi as nuisance parameter
gy2 <- betareg(yield ~ batch + temp, data = GasolineYield, phi = FALSE)
gy2

## compare reported output
coef(gy1)
coef(gy2)
summary(gy1)
summary(gy2)