The different mechanisms that may influence the probability of a connection between two nodes.

<p>In each of the instances, the distance from node <i>A</i> to <i>B</i> and from node <i>C</i> to <i>B</i> are equal. In figure (a) the link probabilities are determined by the combined radii of the nodes. It is much more likely that nodes <i>B</i> and <i>C</i> will form a link due to their radii. In figure (b), the probably of a link between nodes <i>A</i> and <i>B</i> increases because node <i>A</i> is a hub (i.e. high node degree), even though it still has a small spatial reach. In figure (c), nodes <i>A</i> and <i>B</i> have a high probability of forming a link because they are both in the same community. In contrast the probability of a connection between <i>B</i> and <i>C</i> is reduced because they are in different communities.</p>