degree()#

relationalai.std.graphs.Compute
degree(node: Producer) -> Expression

Compute the degree of a node. For an undirected graph, the degree of a node is the number of neighbors it has in the graph. In a directed graph, the degree of a node is the sum of its indegree and outdegree. Must be called in a rule or query context.

Supported Graph Types#

Graph TypeSupportedNotes
DirectedYes
UndirectedYes
WeightedYesWeights are ignored.
UnweightedYes

Parameters#

NameTypeDescription
nodeProducerA node in the graph.

Returns#

Returns an Expression object that produces the degree of the node as an integer value.

Example#

Use .degree() to compute the degree of a node in a graph. You access the .degree() method from a Graph object’s .compute attribute:

import relationalai as rai
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 graph and connect them with a 'friends' property.
with model.rule():
    alice = Person.add(name="Alice")
    bob = Person.add(name="Bob")
    alice.friends.add(bob)
    bob.friends.add(alice)

# Create an undirected graph with Person nodes and edges between friends.
# This graph has one edge between Alice and Bob.
graph = Graph(model, undirected=True)
graph.Node.extend(Person)
graph.Edge.extend(Person.friends)

# Get the number of nodes in the graph.
with model.query() as select:
    # Get all Person objects.
    person = Person()
    # Compute the degree of each person.
    degree = graph.compute.degree(person)
    # Select the name of each person and their degree.
    response = select(person.name, degree)

print(response.results)
# Output:
#     name  v
# 0  Alice  1
# 1    Bob  1

In directed graphs, the degree of a node is the sum of its indegree and outdegree:

# Create a directed graph with Person  nodes and edges between friends.
# Note that graphs are directed by default.
# This graph has two edges. One from Alice to Bob and one from Bob to Alice.
directed_graph = Graph(model)
directed_graph.Node.extend(Person)
directed_graph.Edge.extend(Person.friends)

# Get the degree of each person in the graph.
with model.query() as select:
    person = Person()
    degree = directed_graph.compute.degree(person)
    response = select(person.name, degree)

print(response.results)
# Output:
#     name  v
# 0  Alice  2
# 1    Bob  2

See Also#