Table 2.

Summary of network-based features

Features	Definitiona
Common neighbors	|N(Pi) ∩ N(Pj)|
Jaccard index	$\frac{\left|N\left(P_i\right)\cap N\left(P_j\right)\right|}{\left|N\left(P_i\right)\cup N\left(P_j\right)\right|}$
Adamic–Adar index	$\sum _{P_k\in N\left(P_i\right)\cap N\left(P_j\right)}\frac{1}{log\left|N\left(P_k\right)\right|}$
Preferential attachment score	|N(Pi)| × |N(Pj)|
Otsuka–Ochiai coefficient	$\frac{\left|N\left(P_i\right)\cap N\left(P_j\right)\right|}{\sqrt{\left|N\left(P_i\right)\times N\left(P_j\right)\right|}}$

^aN(P_i) denotes the set of P_i’s neighbors