public List <Suggestion> GetSuggest(UserBehavior db, long userId)
{
IRater rater = new SimpleRater();
IComparer comparer = new CorrelationUserComparer();
recommender = new ItemCollaborativeFilterRecommender(comparer, rater, 50);
recommender.Train(db);
var suggestion = recommender.GetSuggestions(userId, 500);
return(suggestion);
}
public static TestResults Test(this IRecommender classifier, UserBehaviorDatabase db, int numSuggestions)
{
// We're only using the ratings to check for existence of a rating, so we can use a simple rater for everything
SimpleRater rater = new SimpleRater();
UserBehaviorTransformer ubt = new UserBehaviorTransformer(db);
UserArticleRatingsTable ratings = ubt.GetUserArticleRatingsTable(rater);
int correctUsers = 0;
double averagePrecision = 0.0;
double averageRecall = 0.0;
// Get a list of users in this database who interacted with an article for the first time
List <int> distinctUsers = db.UserActions.Select(x => x.UserID).Distinct().ToList();
var distinctUserArticles = db.UserActions.GroupBy(x => new { x.UserID, x.ArticleID });
// Now get suggestions for each of these users
foreach (int user in distinctUsers)
{
List <Suggestion> suggestions = classifier.GetSuggestions(user, numSuggestions);
bool foundOne = false;
int userIndex = ratings.UserIndexToID.IndexOf(user);
int userCorrectArticles = 0;
int userTotalArticles = distinctUserArticles.Count(x => x.Key.UserID == user);
foreach (Suggestion s in suggestions)
{
int articleIndex = ratings.ArticleIndexToID.IndexOf(s.ArticleID);
// If one of the top N suggestions is what the user ended up reading, then we're golden
if (ratings.Users[userIndex].ArticleRatings[articleIndex] != 0)
{
userCorrectArticles++;
if (!foundOne)
{
correctUsers++;
foundOne = true;
}
}
}
averagePrecision += (double)userCorrectArticles / numSuggestions;
averageRecall += (double)userCorrectArticles / userTotalArticles;
}
averagePrecision /= distinctUsers.Count;
averageRecall /= distinctUsers.Count;
return(new TestResults(distinctUsers.Count, correctUsers, averageRecall, averagePrecision));
}