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Analysing spatial point patterns in R - CSIRO

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22.2 Cox processes 141<br />

22.2 Cox processes<br />

A Cox <strong>po<strong>in</strong>t</strong> process is effectively a Poisson process with a random <strong>in</strong>tensity function. Let Λ(u)<br />

be a random function with non-negative values, def<strong>in</strong>ed at all locations u ∈ R 2 . Conditional on<br />

Λ, let X be a Poisson process with <strong>in</strong>tensity function Λ. Then X is a Cox process.<br />

A trivial example is the “mixed Poisson” process <strong>in</strong> which we generate a random variable Λ<br />

and, conditional on Λ, generate a uniform Poisson process with <strong>in</strong>tensity Λ. Follow<strong>in</strong>g are three<br />

different realisations of this process:<br />

> par(mfrow = c(1, 3))<br />

> for (i <strong>in</strong> 1:3) {<br />

+ lambda plot(rMaternI(70, 0.05))<br />

Copyright<strong>CSIRO</strong> 2010

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