rnegbin {MASS}  R Documentation 
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"))
n 
If a scalar, the number of sample values required. If a vector,

mu 
The vector of means. Short vectors are recycled. 
theta 
Vector of values of the 
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.
Vector of random Negative Binomial variate values.
Changes .Random.seed
in the usual way.
# Negative Binomials with means fitted(fm) and theta = 4.5
fm < glm.nb(Days ~ ., data = quine)
dummy < rnegbin(fitted(fm), theta = 4.5)