Decision tree. A decision tree obtained on the protein-protein interaction network using expression data, phylogenetic profiles and localization data as inputs. The tree size was determined by cost-complexity pruning with 10-fold cross-validation. The left (resp. right) edge from a test node corresponds to the test of the node being true (resp. false). Each leaf is labeled with a pair (N, p), where N is the number of proteins in its cluster and p is the percentage of protein pairs that interact in the cluster.