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 Type | Supported | Notes |
---|---|---|
Directed | Yes | |
Undirected | Yes | |
Weighted | Yes | Weights are ignored. |
Unweighted | Yes |
Parameters#
Name | Type | Description |
---|---|---|
node | Producer | A 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