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Negative Binomial for mcp

Source: R/families.R
negbinomial.Rd

Parameterized as mu (the conditional mean) and shape (the same quantity as size in rnbinom()). Thus Var(y) = mu + mu^2 / shape, which approaches the Poisson variance as shape approaches infinity.

Usage

negbinomial(link = "log", link_shape = "log")

Arguments

Link function for mu.

Link function for shape.

Details

shape(1) is added implicitly and is constant across segments unless a shape() formula is supplied. For example, y ~ 1 + x + shape(1 + x) models both the mean and shape. Regression coefficients for both dpars are on their link scales.