Provides "people you should follow" or other graph-based recommendations. By calling the suggest method and providing two data fetching methods for looking up forward connections (ie "users followed by a user") and reverse connections (ie "users following a user") you can get back a list of suggested friends, products, or any other concept that can be represented as a graph.
Use NPM to install:
npm install graph-suggestions
A simple example showing the behavior of the forwardOnly option.
var suggestions = require('graph-suggestions');
var DATA_STORE = {
Andrew: { friends: [ 'Ben' ] },
Ben: { friends: [ 'Andrew', 'Chuck' ] },
Chuck: { friends: [ 'Ben' ] },
Dennis: { friends: [ 'Andrew' ] }
};
var opts = { forwardOnly: true, forwardConnections: forwardFetcher };
suggestions.suggest('Andrew', opts, function(err, results) {
if (err) throw err;
// Forward-Only: [{"nodeID":"Chuck","score":0.0625}]
console.log('Forward-Only: ' + JSON.stringify(results));
});
opts = { forwardConnections: forwardFetcher, reverseConnections: reverseFetcher };
suggestions.suggest('Andrew', opts, function(err, results) {
if (err) throw err;
// Bi-Directional: [{"nodeID":"Dennis","score":0.111},{"nodeID":"Chuck","score":0.0417}]
console.log('Bi-Directional: ' + JSON.stringify(results));
});
function forwardFetcher(nodeID, callback) {
var node = DATA_STORE[nodeID];
callback(null, node ? node.friends : []);
}
function reverseFetcher(nodeID, callback) {
var array = [];
for (var curNodeID in DATA_STORE) {
var node = DATA_STORE[curNodeID];
if (node.friends.indexOf(nodeID) !== -1)
array.push(curNodeID);
}
callback(null, array);
}The algorithm used under the hood is Personalized PageRank. Starting from a given node, the graph is traversed a given number of degrees outward (defaulting to three). There are many great resources online describing PageRank and Personalized PageRank, but a quick summary is that nodes will be scored based on your likelihood to stumble upon them on a random walk through your local graph. A forwardOnly setting (defaulting off) toggles whether this random walk can follow directed edges in the reverse direction or not. If you have an undirected graph such as a Facebook-style symmetric friendship graph, you'll want to set forwardOnly to true to avoid redundant work.
The implementation is based on a blog post by Edwin Chen detailing a solution for Facebook's user recommendation challenge.