Distribution of prominence values in eigenvectors. (a) Hubs & Authorities (b) PageRank. The prominence values were derived from the principal eigenvector of the connectivity matrix that was generated from focused subgraph with the protein query ubiquitin. Sparse models assign high value to the protein family ubiquitin-protein ligase, ubiquitin-activating enzyme (docid: 5977355), and medium values to its 131 members. All other nodes are given values less than 0.02. Similar patterns of prominence values are observed in other eigenspaces and for other queries. On the other hand, PageRank consolidates the top-scoring documents from multiple eigenspaces of the other methods, resulting in a smoother distribution of prominence values.