snbinom {WALS}

Internal function: first derivatives of NB2 PMF

Description

First derivatives of NB2 PMF used in fitNB2. Code is taken from the function snbinom() in the countreg package version 0.2-1 (2023-06-13) (Zeileis and Kleiber 2023).

Usage

snbinom(x, mu, size, parameter = c("mu", "size"), drop = TRUE)

Arguments

x

Vector of quantiles.

mu

Vector of means.

size

Vector of dispersion parameter. If a scalar is given, the value is recycled.

parameter

Specifies which parameter the derivative is taken for. parameter = c("mu", "size") returns a matrix with derivatives for both parameters.

drop

If TRUE, drops empty dimensions of return using drop. If FALSE does not apply drop.

Value

A vector or matrix containing the first derivatives.

References

Zeileis A, Kleiber C (2023). countreg: Count Data Regression. R package version 0.2-1, https://r-forge.r-project.org/projects/countreg/.