extra.parameter: Procedure to Select the Extra Parameter for PLreg Objects

Description

The extra.parameter function is used to select the extra parameter of some power logit models. It provides plots of -2logLik and the Upsilon measure (see Queiroz and Ferrari (2022)) versus \(\zeta\), the extra parameter.

Usage

extra.parameter(object, lower, upper, grid = 10, graph = TRUE)

Value

extra.parameter returns a list with five objects:

zeta.Ups: The selected zeta based on the Upsilon measure.
zeta.loglik: The selected zeta based on -2logLik.
zeta.values: The values of zeta used in the graphs.
Upsilon.values: -2logLik evaluated at each value of zeta.
loglik.values: Upsilon measure evaluated at each value of zeta.

Arguments

object: fitted model object of class "PLreg".
lower: a numeric value representing the lower limit of the interval for the extra parameter.
upper: a numeric value representing the upper limit of the interval for the extra parameter.
grid: a positive integer representing the number of points in the plots. Default is grid=10. If grid is less than 10, then grid=10.
graph: logical. If graph = TRUE the plots are shown, if graph = FALSE the plots are not shown. Default is graph = TRUE.

References

Queiroz, F. F. and Ferrari, S. L. P. (2022). Power logit regression for modeling bounded data. arXiv:2202.01697.

Examples

Run this code

data("bodyfat_Aeolus")

#Initial model with zeta = 2
fit1 <- PLreg(percentfat ~ days + sex + year, data = bodyfat_Aeolus,
             family = "PE", zeta = 2)
summary(fit1)
# Choosing the best value for zeta
# \donttest{
extra.parameter(fit1, lower = 1, upper = 4, grid = 15)# }