The simplest formulation is a set X = {x ∈ D} where D, which can be called the 'study region,' is a subset of Rn, a n-dimensional Euclidean space.
The easiest way to visualize a 2-D point pattern is a map of the locations, which is simply a scatterplot but with the provision that the axes are equally scaled.
An empirical definition of D would be the convex hull of the points, or at least their bounding box, a matrix of the ranges of the coordinates.
Popular models are those based on simple circles and ellipses, inter-point (and especially nearest neighbor) distances, quadrats, and intensity functions.
PPA has applications in a wide range of areas, including astronomy, archaeology,[2][3] geography, ecology, biology, and epidemiology.