13.5 Poisson Distribution
13.5.1 Probability Mass Function
If \(\lambda \in \mathbb{R}^+\), then for \(n \in \mathbb{N}\), \[ \text{Poisson}(n|\lambda) = \frac{1}{n!} \, \lambda^n \, \exp(-\lambda). \]
13.5.2 Sampling Statement
n ~ poisson(lambda)
Increment target log probability density with poisson_lpmf( n | lambda)
dropping constant additive terms.
13.5.3 Stan Functions
real poisson_lpmf(ints n | reals lambda)
The log Poisson probability mass of n given rate lambda
real poisson_cdf(ints n, reals lambda)
The Poisson cumulative distribution function of n given rate lambda
real poisson_lcdf(ints n | reals lambda)
The log of the Poisson cumulative distribution function of n given
rate lambda
real poisson_lccdf(ints n | reals lambda)
The log of the Poisson complementary cumulative distribution function
of n given rate lambda
R poisson_rng(reals lambda)
Generate a Poisson variate with rate lambda; may only be used in
generated quantities block. lambda must be less than \(2^{30}\). For a
description of argument and return types, see section
vectorized function signatures.