Find Friends of Friends in Social Neighborhood

Connect to Neo4j Database

Create a Neo4j connection object neo4jconn using the URL http://localhost:7474/db/data, user name neo4j, and password matlab.

url = 'http://localhost:7474/db/data';
username = 'neo4j';
password = 'matlab';

neo4jconn = neo4j(url,username,password);

Check the Message property of the Neo4j connection object neo4jconn. The blank Message property indicates a successful connection.

neo4jconn.Message

ans =

     []

Search for One Person in Database

Find the node that has the node label Person with the property name User1.

user1 = searchNode(neo4jconn,'Person','PropertyKey','name', ...
    'PropertyValue','User1')

user1 = 
  Neo4jNode with properties:

        NodeID: 0
      NodeData: [1×1 struct]
    NodeLabels: 'Person'

Search for All Second-Degree Friends of Person

Find outgoing relationships for User1. To limit the search to relationships with a distance of two or less, specify 2 as the value of the name-value pair argument 'Distance'.

user1_relation = searchRelation(neo4jconn,user1,'out','Distance',2)

user1_relation = struct with fields:
       Origin: 0
        Nodes: [4×3 table]
    Relations: [4×5 table]

Convert Graph Data to Directed Graph

Using the table user1_relation.Nodes, access the name property for each node that appears in the NodeData variable of the table.

Assign the table user1_relation.Nodes to nodestable.

nodestable = user1_relation.Nodes

nodestable=4×3 table
         NodeLabels      NodeData                  NodeObject             
         __________    ____________    ___________________________________

    0     'Person'     [1×1 struct]    [1x1 database.neo4j.http.Neo4jNode]
    1     'Person'     [1×1 struct]    [1x1 database.neo4j.http.Neo4jNode]
    2     'Person'     [1×1 struct]    [1x1 database.neo4j.http.Neo4jNode]
    3     'Person'     [1×1 struct]    [1x1 database.neo4j.http.Neo4jNode]

Assign the row names for each row in the table nodestable to rownames.

rownames = nodestable.Properties.RowNames

rownames = 4×1 cell array
    {'0'}
    {'1'}
    {'2'}
    {'3'}

Access the NodeData variable from nodestable for each row. nodedata contains an array of structures.

nodedata = [nodestable.NodeData{rownames}]

nodedata = 1×4 struct array with fields:
    name

To retrieve the name field from each structure, index into the array. nodenames is a cell array of character vectors that contains node names.

nodenames = {nodedata(:).name}

nodenames = 1×4 cell array
    {'User1'}    {'User3'}    {'User2'}    {'User4'}

Create the digraph object user1_graph using the neo4jStruct2Digraph function with the relationship data stored in user1_relation and the node names stored in nodenames.

user1_graph = neo4jStruct2Digraph(user1_relation,'NodeNames',nodenames)

user1_graph = 
  digraph with properties:

    Edges: [4×3 table]
    Nodes: [4×3 table]

To see a visual representation of the graph, create a figure that displays user1_graph.

plot(user1_graph,'EdgeLabel',user1_graph.Edges.RelationType)

Find Friends of Person

Retrieve a list of all the first-degree friends of User1. The user1_friend variable is a cell array of character vectors that contains the names of first-degree friends.

disp('Friends of User1 are:')

Friends of User1 are:

user1_friend = successors(user1_graph,'User1')

user1_friend = 2×1 cell array
    {'User3'}
    {'User2'}

Find Second-Degree Friends

To find the second-degree friends of User1, run successors again by looping through the list of the first-degree friends. user1_friends_friend is a cell array of character vectors that contains the names of second-degree friends.

user1_friends_friend = {};
for i = 1:length(user1_friend)
    user1_friends_friend = [user1_friends_friend; ...
        successors(user1_graph,user1_friend{i})]; 
end
disp('Friends of User1''s friends are:')

Friends of User1's friends are:

user1_friends_friend = unique(user1_friends_friend)

user1_friends_friend = 2×1 cell array
    {'User3'}
    {'User4'}

Remove Duplicate Friends

Remove duplicates from the second-degree friends list that are already in the first-degree friends list using setdiff.

finalResult = setdiff(user1_friends_friend,user1_friend);

disp('User1''s second-degree friends are:')

User1's second-degree friends are:

for i = 1:length(finalResult)
    disp(finalResult{i})
end

User4

finalResult is a cell array of character vectors that contains the names of second-degree friends. This list removes the names of the first-degree friends.

Close Database Connection

close(neo4jconn)