Simulate Negative Binomial Variates

Function to generate random outcomes from a Negative Binomial distribution, with mean mu and variance mu + mu^2/theta.

rnegbin(n, mu = n, theta = stop("'theta' must be specified"))

Arguments

n

If a scalar, the number of sample values required. If a vector, length(n) is the number required and n is used as the mean vector if mu is not specified.

mu

The vector of means. Short vectors are recycled.

theta

Vector of values of the theta parameter. Short vectors are recycled.

Value

Vector of random Negative Binomial variate values.

Side Effects

Changes .Random.seed in the usual way.

Details

The function uses the representation of the Negative Binomial distribution as a continuous mixture of Poisson distributions with Gamma distributed means. Unlike rnbinom the index can be arbitrary.

Examples

# Negative Binomials with means fitted(fm) and theta = 4.5
fm <- glm.nb(Days ~ ., data = quine)
dummy <- rnegbin(fitted(fm), theta = 4.5)