negbin1 {addreg}

Family Functions for Negative Binomial 1 Models

Description

Specifies the information required to fit a negative binomial 1 (NB1) model.

Usage

negbin1(link, phi = stop("'phi' must be given"))

Arguments

link

included for compatibility with family. For addreg models, this will always be "identity".

phi

the value of the scale parameter of the NB1 distribution (see "Details"). This can be set to NA for initialisation, but during estimation the family should be updated with the current estimate, and must be strictly positive.

Details

The NB1 distribution can be parameterised in terms of a mean \mu and scale parameter \phi (the phi argument of this function), such that if Y \sim NB1(\mu, \phi), then E(Y) = \mu and Var(Y) = (1+\phi)\mu.

These can be related to the size and prob arguments of the NegBinomial functions by size = \mu / \phi and prob = 1 / (1 + \phi).

Value

An object of class "family": see family for full details. Note that when the estimate of phi is updated in a model, this family object must be reloaded using the new estimate.

Author(s)

Mark W. Donoghoe [e-mail]