recommendation example

cypher.rb

recommend = Neo4j.query do
   node(alice).where_not{|me| me > ':follows' > :user} > ':used_tag' > :tag < ':used_tag' < :user
   ret(node(:user), count(:tag).desc(count(:tag)))
end.first[:user]

cypher_test.rb

require 'rubygems'
require 'neo4j-core'

tx = Neo4j::Transaction.new
alice = Neo4j::Node.new(:name => 'Alice')
ted = Neo4j::Node.new(:name => 'Ted')
carol = Neo4j::Node.new(:name => 'Carol')
bob = Neo4j::Node.new(:name => 'Bob')

alice.outgoing(:follows) << ted

neo4j = Neo4j::Node.new(:name => '#neo4j')
rails = Neo4j::Node.new(:name => '#rails')
jruby = Neo4j::Node.new(:name => '#jruby')

rails.incoming(:used_tag) << alice << carol << bob
neo4j.incoming(:used_tag) << alice << ted << bob
jruby.incoming(:used_tag) << ted << carol << bob

tx.success
tx.finish

puts "query"

recommend = Neo4j.query do
   node(alice).where_not{|me| me > ':follows' > :user} > ':used_tag' > :tag < ':used_tag' < :user
   ret(node(:user), count(:tag).desc(count(:tag)))
end.first[:user]

puts "Recommend #{recommend[:name]}"

#puts "result.columns=#{result.columns.inspect}"
#x = result.to_a
#puts "X=#{x.size}"
#x.each do |r|
#  puts "user name #{r[:'user.name']}"
#end

recommend.rb

tags = alice.outgoing(:used_tags).to_a
my_followers = alice.outgoing(:follows).to_a
# find other users which also used the same tags as me but are not already my followers
other_users =alice.outgoing(:used_tags).incoming(:used_tags).depth(2).filter{|path| path.length == 2 && !my_followers.include?(path.end_node)}

# for all those users, find the user who has the maximum number of similar tags as I have
recommend = other_users.max_by{|friend| (friend.outgoing(:used_tags).to_a & tags).size }

todo.txt

(1) {"name":"Alice"}
(2) {"name":"Ted"}
(3) {"name":"Carol"}
(4) {"name":"Bob"}
(5) {"name":"#neo4j"}
(6) {"name":"#rails"}
(7) {"name":"#jruby"}
(1)-[:used_tag]->(6)
(4)-[:used_tag]->(6)
(3)-[:used_tag]->(6)
(1)-[:used_tag]->(5)
(2)-[:used_tag]->(5)
(4)-[:used_tag]->(5)
(3)-[:used_tag]->(7)
(2)-[:used_tag]->(7)
(4)-[:used_tag]->(7)
(1)-[:follows]->(2)

start alice=node(1) MATCH alice-[:used_tag]->(tag)<-[:used_tag]-user WHERE not(alice-[:follows]-user) RETURN user.name, count(tag) ORDER BY count(tag) DESC

http://console.neo4j.org/?init=%281%29%20{%22name%22%3A%22Alice%22}%0A%282%29%20{%22name%22%3A%22Ted%22}%0A%283%29%20{%22name%22%3A%22Carol%22}%0A%284%29%20{%22name%22%3A%22Bob%22}%0A%285%29%20{%22name%22%3A%22%23neo4j%22}%0A%286%29%20{%22name%22%3A%22%23rails%22}%0A%287%29%20{%22name%22%3A%22%23jruby%22}%0A%281%29-[%3Aused_tag]-%3E%286%29%0A%284%29-[%3Aused_tag]-%3E%286%29%0A%283%29-[%3Aused_tag]-%3E%286%29%0A%281%29-[%3Aused_tag]-%3E%285%29%0A%282%29-[%3Aused_tag]-%3E%285%29%0A%284%29-[%3Aused_tag]-%3E%285%29%0A%283%29-[%3Aused_tag]-%3E%287%29%0A%282%29-[%3Aused_tag]-%3E%287%29%0A%284%29-[%3Aused_tag]-%3E%287%29%0A%281%29-[%3Afollows]-%3E%282%29&query=start%20alice%3Dnode%281%29%20MATCH%20alice-[%3Aused_tag]-%3E%28tag%29%3C-[%3Aused_tag]-user%20WHERE%20not%28alice-[%3Afollows]-user%29%20RETURN%20user.name%2C%20count%28tag%29%20ORDER%20BY%20count%28tag%29%20DESC&version=&no_root=true


http://tinyurl.com/7zzad7t