Like I promised in my previous post, I wanted to do a little something on D3.js.
We are going to take one of their example visualizations and visualize a follows graph.
To create our graph, we will take the names of 20 people: create nodes for them, add them to an index, and randomly link them together.
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I done wrestled with an alligator, I done tussled with a whale, only last week I murdered a rock, injured a stone, hospitalized a brick. I’m so mean I make medicine sick.
He floats like a butterfly and stings like a bee, but is Muhammad Ali truly the greatest? Greater than the Beatles? Greater than Alexander? Greater than Sliced Bread? Let’s find out.
We begin by requiring neography and creating a function to help us create the greats.
require 'rubygems'
require 'neography'
def create_great(name)
Neography::Node.create("name" => name)
end
There are a ton of greats out there, but we’ll keep it simple and create just 8 of the greatest greats.
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We had our first Graph Database Meet-up in Chicago yesterday!
16 Graphistas came out to learn more about the craft and get an introduction to Neo4j. Ryan Briones from Groupon gave us a venue and helped host the event. No worries if you missed it, your next chance to learn more about Neo4j is coming up on Tuesday February 7th @ 6pm, when Prasanna Pendse will share his experiences with Neo4j at ChicagoRuby: Downtown.
Our next Chicago Graph DB meet-up is tentatively scheduled for February 29th @ 6 pm. This will be a hands-on meet-up. I’ll help you get started with either Neo4j on your laptop or in the cloud with Heroku. We’ll create a few graphs, learn some basic traversals and get comfortable with Neo4j. I’ll have a GitHub repository graph for us to play with and see how you are connected to Kevin Bacon (err I mean Linus Torvalds). He is the center of the GitHub universe right? Right? We’ll let’s find out.
The slides of our first meet-up are available below:
This week we learned that leaving the create_graph method accessible to the world was a bad idea. So let’s go ahead and delete that route in Sinatra, and instead create a Rake Task for it.
In Rakefile:
require 'neography/tasks'
require './neoflix.rb'
namespace :neo4j do
task :create do
neo = Neography::Rest.new(ENV['NEO4J_URL'] || "http://localhost:7474")
create_graph(neo)
end
end
That’s much better. We can create our graph locally with
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So far we’ve learned how to get Neo4j up and running with Neography, how to find friends of friends and degrees of separation with the Neo4j REST API and a little bit of the Gremlin and Cypher languages. However, all we’ve seen is text output. We haven’t really “seen” a graph yet, but that’s about to change.
Vouched holds a graph of skill specific recommendations people have made to each other and visualizes it. I extracted the visualization, and hosted it on github as neovigator. You can get your very own visualization up and running or take a look at this instance running on Heroku.
Cypher is the query language of Neo4j, and as promised I’ll show you how you can use it to implement friend recommendations as well as degrees of separation.
We can send any cypher query to Neo4j via the REST API and neography using the execute_query command. Let’s implement suggestions_for so it sends a cypher query to the server:
def suggestions_for(node)
node_id = node["self"].split('/').last.to_i
@neo.execute_query("START me = node({node_id})
MATCH (me)-[:friends]->(friend)-[:friends]->(foaf)
RETURN foaf.name", {:node_id => node_id})["data"]
end
puts "Johnathan should become friends with #{suggestions_for(johnathan).join(', ')}"
# RESULT
# Johnathan should become friends with Mary, Phil
Gremlin is a domain specific language for traversing property graphs. Neo4j is one of the databases that can speak the gremlin language, and as promised I’ll show you how you can use it to implement friend recommendations as well as degrees of separation.
We can send any gremlin script to Neo4j via the REST API and neography using the execute_script command. Let’s implement suggestions_for so it sends a gremlin script to the server:
def suggestions_for(node)
node_id = node["self"].split('/').last.to_i
@neo.execute_script("g.v(node_id).
in('friends').
in('friends').
dedup.
filter{it != g.v(node_id)}.
name", {:node_id => node_id})
end
puts "Johnathan should become friends with #{suggestions_for(johnathan).join(', ')}"
# RESULT
# Johnathan should become friends with Mary, Phil
Getting started with Ruby and Neo4j is very easy.
Follow these steps and you’ll be up and running in no time.
First we install the neography gem:
Using Bundler:
echo "source 'http://rubygems.org' gem 'neography' " > Gemfile bundle install
Without Bundler:
gem install neography
Then we’ll add our tasks to a Rakefile, download Neo4j and start it:
echo "require 'neography/tasks'" > Rakefile rake neo4j:install rake neo4j:start
Max De Marzi 