Compute anomaly-tail Poisson probability

Calculates the complementary cumulative distribution function (CCDF) of a Poisson distribution with rate parameter \(\lambda\), starting from a threshold \(q\). This function is designed to evaluate the probability of observing \(n \ge q\) anomalies in a cluster, normalized so that \(P(n \ge 1) = 1\) when \(\lambda\) is used.

Usage

ppois.anom(q, lambda)

Arguments

q

An integer or vector of integers representing the number of observed anomalies.

lambda

A positive numeric value representing the expected number of anomalies (\(\lambda\)).

Value

A numeric vector of normalized CCDF values \(P(n \ge q \mid \lambda)\).