ztpois: Zero-truncated Poisson distribution

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

Zero-truncated Poisson distribution

Description

Probability mass function, distribution function, and random generation for the zero-truncated Poisson distribution.

Usage

dztpois(x, lambda, log = FALSE)

pztpois(q, lambda, lower.tail = TRUE, log.p = FALSE)

rztpois(n, lambda)

Arguments

x, q	integer vector of counts
lambda	vector of (non-negative) means
log, log.p	logical; return log-density if TRUE
lower.tail	logical; if TRUE, probabilities are P[X \le x], otherwise, P[X > x].
n	number of random values to return.

Details

This implementation allows for automatic differentiation with RTMB.

By definition, this distribution only has support on the positive integers (1, 2, ...). Any zero-truncated distribution is defined as

P(X=x | X>0) = P(X=x) / (1 - P(X=0)),

where P(X=x) is the probability mass function of the corresponding untruncated distribution.

Value

dztpois gives the probability mass function, pztpois gives the distribution function, and rztpois generates random deviates.

Examples

set.seed(123)
x <- rztpois(1, 0.5)
d <- dztpois(x, 0.5)
p <- pztpois(x, 0.5)

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