The '''avoidance function'''<ref name="DaleyVere-Jones2007page25"/> or '''void probability'''<ref name="ChiuStoyan2013page110">{{cite book|author1=Sung Nok Chiu|author2=Dietrich Stoyan|author3=Wilfrid S. Kendall|author4=Joseph Mecke|title=Stochastic Geometry and Its Applications|url=https://books.google.com/books?id=825NfM6Nc-EC|date=27 June 2013|publisher=John Wiley & Sons|isbn=978-1-118-65825-3|page=100}}</ref> <math>\textstyle v</math> of a point process <math>\textstyle {N}</math> is defined in relation to some set <math>\textstyle B</math>, which is a subset of the underlying space <math>\textstyle \mathbb{R}^d</math>, as the probability of no points of <math>\textstyle {N}</math> existing in <math>\textstyle B</math>. More precisely,<ref name="ChiuStoyan2013page42">{{cite book|author1=Sung Nok Chiu|author2=Dietrich Stoyan|author3=Wilfrid S. Kendall|author4=Joseph Mecke|title=Stochastic Geometry and Its Applications|url=https://books.google.com/books?id=825NfM6Nc-EC|date=27 June 2013|publisher=John Wiley & Sons|isbn=978-1-118-65825-3|page=42}}</ref> for a test set <math>\textstyle B</math>, the avoidance function is given by:
