Figure 1:

Biomedical networks are characterized by nonuniform degree distributions. Eight degree distributions are plotted for 6 edge types, Hetionet v1.0 [5]. Hetionet integrates subnetworks for 24 different edge types, the degree distributions of which are analyzed separately. Furthermore, bipartite (e.g., Anatomy→expresses→Gene) and directed (e.g., Gene→regulates→Gene) graphs (Hetionet edge types) have both source and target degrees that must be assessed separately. Undirected edge types (e.g., Compound–resembles–Compound) have only a single degree distribution. Degree distributions are nonuniform and vary greatly between different networks. The y-axis is log₁₀-scaled to accommodate the common occurrence where most nodes have low degree while a small portion of nodes have high degree. Several distributions have nodes that reach the maximum degree, corresponding to a node being connected to all other possible nodes. Zero-degree nodes are not displayed, since methodological limitations often result in edge data only existing for a subset of nodes.