adamic_adar(node1: Producer, node2: Producer) -> Expression

Compute the Adamic-Adar index between two nodes in a graph. The Adamic-Adar index quantifies node similarity based on shared neighbors. Values are non-negative. In link prediction analysis, a high Adamic-Adar values may indicate that two nodes are likely to form a connection if they do not already have one. Must be called in a rule or query context.

Supported Graph Types#

Graph TypeSupportedNotes
WeightedYesWeights are ignored.


node1ProducerA node in the graph.
node2ProducerA node in the graph.


Returns an Expression object that produces the Adamic-Adar index between the two nodes as a floating-point value, calculated by the following formula:

Adamic-Adar index = sum(1 / log(degree of shared neighbor))

The sum is over all shared neighbors of the two nodes.


Use .adamic_adar() to compute the Adamic-Adar index between two nodes in a graph. You access the .adamic_adar() method from a Graph object’s .compute attribute:

import relationalai as rai
from relationalai.std import alias
from relationalai.std.graphs import Graph

# Create a model named "socialNetwork" with a Person type.
model = rai.Model("socialNetwork")
Person = model.Type("Person")

# Add some people to the model and connect them with a multi-valued `friend` property.
with model.rule():
    alice = Person.add(name="Alice")
    bob = Person.add(name="Bob")
    carol = Person.add(name="Carol")
    alice.friends.extend([bob, carol])

# Create an undirected graph with Person nodes and edges between friends.
# This graph has two edges: one between Alice and Bob, and one between Bob and Carol.
graph = Graph(model, undirected=True)

# Compute the Adamic-Adar index between each pair of people in the graph.
with model.query() as select:
    person1, person2 = Person(), Person()
    similarity = graph.compute.adamic_adar(person1, person2)
    response = select(,, alias(similarity, "adamic_adar"))

# Output:
#     name  name2  adamic_adar
# 0  Alice  Alice          inf
# 1    Bob    Bob     1.442695
# 2    Bob  Carol     1.442695
# 3  Carol    Bob     1.442695
# 4  Carol  Carol     1.442695

There is no row for Alice and Bob in the preceding query’s results. That’s because Alice and Bob have a an Adamic-Adar index of 0.0. Pairs of nodes with zero index, indicating no meaningful similarity, are often excluded from analyses. Consequently, we filter out these pairs to improve performance.

If node1 or node2 is not a node in the graph, no exception is raised. Instead, that object is filtered from the rule or query:

# Add a Company type to the model.
Company = model.Type("Company")

# Add some companies to the model.
with model.rule():
    apple = Company.add(name="Apple")
    google = Company.add(name="Google")

# Create the union of the Person and Company types.
PersonOrCompany = Person | Company

with model.query() as select:
    # Get all person and company objects.
    obj1, obj2 = PersonOrCompany(), PersonOrCompany()
    obj1 < obj2  # Ensure pairs are unique. Compares internal object IDs.
    # Compute the Adamic-Adar index between each pair of objects.
    # Objects that are not nodes in the graph are filtered.
    similarity = graph.compute.adamic_adar(obj1, obj2)
    response = select(,, alias(similarity, "adamic_adar"))

# Only rows for people are returned, since companies are not nodes in the graph.
# Output:
#     name name2  adamic_adar
# 0  Carol   Bob     1.442695

See Also#