skellam: Skellam distribution

In RTMBdist: Distributions Compatible with Automatic Differentiation by 'RTMB'

Skellam distribution

Description

Probability mass function, distribution function, and random generation for the Skellam distribution.

Usage

dskellam(x, mu1, mu2, log = FALSE)

rskellam(n, mu1, mu2)

Arguments

x	integer vector of counts
mu1, mu2	Poisson means
log	logical; return log-density if TRUE
n	number of random values to return.

Details

The Skellam distribution is the distribution of the difference of two Poisson random variables. Specifically, if X_1 \sim \text{Pois}(\mu_1) and X_2 \sim \text{Pois}(\mu_2), then X_1 - X_2 \sim \text{Skellam}(\mu_1, \mu_2).

This implementation of dskellam allows for automatic differentiation with RTMB.

Value

dskellam gives the probability mass function and rskellam generates random deviates.

Examples

x <- rskellam(1, 2, 3)
d <- dskellam(x, 2, 3)

RTMBdist documentation built on April 1, 2026, 5:07 p.m.