Homophily is the tendency for connected nodes to share interests, attributes, behaviors, or group affiliations. It makes graph data relational rather than i.i.d., so node classification must combine node features with neighborhood structure. section 9.2.1
For classification, homophily turns social context into features: a node’s group membership is treated as likely related to the affiliations of its neighbors. This can capture patterns that total degree or generic embeddings miss. section 9.3.1
A practical homophily-aware node-classification pipeline is:
- Represent each node with total degree plus counts of neighbors in relevant groups. section 9.3.1
Karate club classification
A karate club graph labels nodes by their eventual club affiliation. Degree-only vectors produce an f-score of about 0.43, while Node2Vec reaches about 0.64. Replacing these with total degree, Mr. Hi degree, and officer degree raises the reported f-score to about 0.93, illustrating the value of domain-informed homophily features.
