MixWei: Mixture Weibull Curve constructor function

In gestate: Generalised Survival Trial Assessment Tool Environment

Mixture Weibull Curve constructor function

Description

This creates a Curve object for a Mixture Weibull distribution.
Curve objects contain all necessary information to describe a distribution, including functions and parameters describing it.
Parameterisation follows that used by pweibull etc. See Details for more information on parameterisation.

Usage

MixWei(props, alphas, betas = rep(1, length(props)))

Arguments

props	Vector of length x for the probabilities of the two subpopulations. Must sum to 1.
alphas	Vector of length x for the scale parameters for the corresponding subpopulations define by props.
betas	Vector of length x for the shape parameters for the corresponding subpopulations define by props. Default is rep(1,length(props)), i.e. all exponential distributions.

Details

The mixture distribution with scales alpha1 and alpha2 etc, shapes beta1 and beta2 etc, and prevalences p1 and p2 etc has parameterisation:
f(x) = p1 (beta1/alpha1) (x/alpha1)^(beta1-1) exp(- (x/alpha1)^beta1) + p2 (beta2/alpha2) (x/alpha2)^(beta2-1) exp(- (x/alpha2)^beta2)+...
F(x) = p1 (1 - exp(- (x/alpha1)^beta1) + p2 (1 - exp(- (x/alpha2)^beta2)+...

Author(s)

James Bell

Examples

MixWei(props=c(0.8,0.2),alphas=c(100,10),betas=c(1.1,0.9))

gestate documentation built on April 26, 2023, 5:10 p.m.