log_lik_beta_binom: Beta-Binomial Log-Likelihood

In extras: Helper Functions for Bayesian Analyses

Beta-Binomial Log-Likelihood

Description

This parameterization of the beta-binomial distribution uses an expected probability parameter, prob, and a dispersion parameter, theta. The parameters of the underlying beta mixture are alpha = (2 * prob) / theta and beta = (2 * (1 - prob)) / theta. This parameterization of theta is unconventional, but has useful properties when modelling. When theta = 0, the beta-binomial reverts to the binomial distribution. When theta = 1 and prob = 0.5, the parameters of the beta distribution become alpha = 1 and beta = 1, which correspond to a uniform distribution for the beta-binomial probability parameter.

Usage

log_lik_beta_binom(x, size = 1, prob = 0.5, theta = 0)

Arguments

x	A non-negative whole numeric vector of values.
size	A non-negative whole numeric vector of the number of trials.
prob	A numeric vector of values between 0 and 1 of the probability of success.
theta	A non-negative numeric vector of the dispersion for the mixture models (student, gamma-Poisson and beta-binomial).

Value

An numeric vector of the corresponding log-likelihoods.

See Also

Other log_lik_dist: log_lik_bern(), log_lik_binom(), log_lik_gamma_pois_zi(), log_lik_gamma_pois(), log_lik_gamma(), log_lik_lnorm(), log_lik_neg_binom(), log_lik_norm(), log_lik_pois_zi(), log_lik_pois(), log_lik_student()

Examples

log_lik_beta_binom(c(0, 1, 2), 1, 0.5, 0)

extras documentation built on May 31, 2023, 6:22 p.m.