UniMapParameters: Mapping function for univariate distributions

In GAS: Generalized Autoregressive Score Models

Description

Map unrestricted vector of parameters into the proper space. This function transforms the parameters updated using the GAS recursion into their proper space.

Usage

UniMapParameters(Theta_tilde, Dist)

Arguments

Theta_tilde

numeric Vector of reparametrised parameters, see Details.

Dist	character Label of the conditional distribution, see DistInfo.

Details

The order of the parameters is generally: location, scale, skewness, shape, shape2. When the distribution defined by Dist does not have, say, the shape parameter, this should be simply omitted. See also DistInfo for specific distributions.

Value

A numeric vector of parameters.

Author(s)

Leopoldo Catania

Examples

# Map unrestricted parameters for the Student-t distribution.
library("GAS")

Dist = "std"

# Vector of unconditional reparametrised parameters such that,
# Theta = c(0, 1.5 ,7), i.e., location = 0, scale = 1.5,
# degrees of freedom = 7.

# LowerNu() prints the lower bound numerical parameter for the degree
# of freedom, see help(LowerNu).

Theta_tilde = c(0.1, log(1.5), log(7 - LowerNu()))

Theta = UniMapParameters(Theta_tilde, Dist)

Theta

GAS documentation built on Feb. 4, 2022, 5:12 p.m.