dirmult: Dirichlet-multinomial distribution

In RTMBdist: Distributions Compatible with Automatic Differentiation by 'RTMB'

Dirichlet-multinomial distribution

Description

Density and and random generation for the Dirichlet-multinomial distribution.

Usage

ddirmult(x, size, alpha, log = FALSE)

rdirmult(n, size, alpha)

Arguments

x	vector or matrix of non-negative counts, where rows are observations and columns are categories.
size	vector of total counts for each observation. Needs to match the row sums of x.
alpha	vector or matrix of positive shape parameters
log	logical; if TRUE, densities p are returned as \log(p).
n	number of random values to return.

Details

This implementation of ddirmult allows for automatic differentiation with RTMB.

Value

ddirmult gives the density and rdirmult generates random samples.

Examples

# single alpha
alpha <- c(1,2,3)
size <- 10
x <- rdirmult(1, size, alpha)
d <- ddirmult(x, size, alpha)
# vectorised over alpha and size
alpha <- rbind(alpha, 2*alpha)
size <- c(size, 3*size)
x <- rdirmult(2, size, alpha)

RTMBdist documentation built on April 1, 2026, 5:07 p.m.