BAS (version 1.7.1)

tr.beta.binomial: Truncated Beta-Binomial Prior Distribution for Models

Description

Creates an object representing the prior distribution on models for BAS using a truncated Beta-Binomial Distribution on the Model Size

Usage

tr.beta.binomial(alpha = 1, beta = 1, trunc)

Value

returns an object of class "prior", with the family and hyperparameters.

Arguments

alpha

parameter in the beta prior distribution

beta

parameter in the beta prior distribution

trunc

parameter that determines truncation in the distribution i.e. P(M; alpha, beta, trunc) = 0 if M > trunc.

Author

Merlise Clyde

Details

The beta-binomial distribution on model size is obtained by assigning each variable inclusion indicator independent Bernoulli distributions with probability w, and then giving w a beta(alpha,beta) distribution. Marginalizing over w leads to the number of included predictors having a beta-binomial distribution. The default hyperparameters lead to a uniform distribution over model size. The Truncated version assigns zero probability to all models of size > trunc.

See Also

bas.lm, Bernoulli,uniform

Other priors modelpriors: Bernoulli.heredity(), Bernoulli(), beta.binomial(), tr.poisson(), tr.power.prior(), uniform()

Examples

Run this code

tr.beta.binomial(1, 10, 5)
library(MASS)
data(UScrime)
UScrime[, -2] <- log(UScrime[, -2])
crime.bic <- bas.lm(y ~ .,
  data = UScrime, n.models = 2^15, prior = "BIC",
  modelprior = tr.beta.binomial(1, 1, 8),
  initprobs = "eplogp"
)

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