Calculation of the clustering coefficient (<i>C</i>).

<p>The links between node <i>i</i> and other nodes in the network defines the neighborhood of node <i>i</i> (A). Node <i>i</i> has 8 links, or “neighbors”, denoted as <i>k_i</i>. To calculate the clustering coefficient for node <i>i</i> (<i>C_i</i>), we find the number of possible unique connections between the neighbors (<i>k_i</i>) using the formula [<i>k_i</i>(<i>k_i</i>−1)/2], or in this case (8*7)/2 = 28. We then find the number of actual connections (<i>Δ</i>_i) between neighbors, in this case 5 (B). <i>C_i</i> is simply defined as the actual links (<i>Δ</i>_i) divided by the possible links [<i>k_i</i>(<i>k_i</i>−1)/2] in the neighborhood of node <i>i</i>. Therefore, <i>C_i</i> = 2<i>Δ</i>_i/(<i>k_i</i>−1)<i>k_i</i> = 0.178 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051074#pone.0051074-Watts1" target="_blank">[40]</a>.