protected List <Rating> GetRecommendations(MyTable ratingTable, MyTable W, int K = 80, int N = 10)
{
MyTable recommendedTable = new MyTable();
foreach (int userId in ratingTable.Keys)
{
Hashtable Nu = (Hashtable)ratingTable[userId]; // ratings of user u
if (!W.ContainsMainKey(userId)) // NOTE: a user bought an item which had only rated by him.
{
continue;
}
List <Link> similarUsers = GetSimilarUsers(W, userId, K);
foreach (Link l in similarUsers)
{
int vId = l.To; // similar user v
Hashtable Nv = (Hashtable)ratingTable[vId]; // ratings of user v
foreach (int iId in Nv.Keys)
{
if (Nu.ContainsKey(iId))
{
continue;
}
if (recommendedTable.ContainsKey(userId, iId))
{
double _t = (double)recommendedTable[userId, iId];
recommendedTable[userId, iId] = _t + l.Weight;
}
else
{
recommendedTable.Add(userId, iId, l.Weight);
}
}
}
}
List <Rating> recommendedItems = new List <Rating>();
foreach (int uId in recommendedTable.Keys)
{
List <Rating> li = new List <Rating>();
Hashtable subTable = (Hashtable)recommendedTable[uId];
foreach (int iId in subTable.Keys)
{
double _t = (double)subTable[iId];
li.Add(new Rating(uId, iId, _t));
}
List <Rating> sortedLi = li.OrderByDescending(r => r.Score).ToList();
recommendedItems.AddRange(sortedLi.GetRange(0, Math.Min(sortedLi.Count, N)));
}
return(recommendedItems);
}
protected MyTable GetRecommendationsByTFIDFPlusPlus(MyTable ratingTable, MyTable userTagTable,
Hashtable tagUsersTable, MyTable tagItemTable, Hashtable itemTagsTable)
{
MyTable recommendTable = new MyTable();
int[] userIds = new int[ratingTable.Keys.Count];
ratingTable.Keys.CopyTo(userIds, 0);
Parallel.ForEach(userIds, userId =>
{
Hashtable subTable = (Hashtable)ratingTable[userId];
if (userTagTable.ContainsMainKey(userId))
{
Hashtable tagTable = (Hashtable)userTagTable[userId];
foreach (int tagId in tagTable.Keys)
{
if (!tagItemTable.ContainsMainKey(tagId))
{
continue;
}
Hashtable itemTable = (Hashtable)tagItemTable[tagId];
foreach (int itemId in itemTable.Keys)
{
// if user has rated this item
if (subTable.ContainsKey(itemId))
{
continue;
}
List <Link> n_b = (List <Link>)tagUsersTable[tagId]; // # of users who used this tag
List <Link> n_i = (List <Link>)itemTagsTable[itemId]; // # of users who used this tag
double wut = (double)tagTable[tagId];
double wti = (double)itemTable[itemId];
double pui = wut / Math.Log(1 + n_b.Count) * wti / Math.Log(1 + n_i.Count);
lock (recommendTable)
{
if (recommendTable.ContainsKey(userId, itemId))
{
recommendTable[userId, itemId] = (double)recommendTable[userId, itemId] + pui;
}
else
{
recommendTable.Add(userId, itemId, pui);
}
}
}
}
}
});
return(recommendTable);
}
protected MyTable GetRecommendations(MyTable ratingTable, MyTable userTagTable, MyTable tagItemTable)
{
MyTable recommendTable = new MyTable();
int[] userIds = new int[ratingTable.Keys.Count];
ratingTable.Keys.CopyTo(userIds, 0);
Parallel.ForEach(userIds, userId =>
{
Hashtable subTable = (Hashtable)ratingTable[userId];
if (userTagTable.ContainsMainKey(userId))
{
Hashtable tagTable = (Hashtable)userTagTable[userId];
foreach (int tagId in tagTable.Keys)
{
if (!tagItemTable.ContainsMainKey(tagId))
{
continue;
}
Hashtable itemTable = (Hashtable)tagItemTable[tagId];
foreach (int itemId in itemTable.Keys)
{
// if user has rated this item
if (subTable.ContainsKey(itemId))
{
continue;
}
double wut = (double)tagTable[tagId];
double wti = (double)itemTable[itemId];
double p = wut * wti;
lock (recommendTable)
{
if (recommendTable.ContainsKey(userId, itemId))
{
recommendTable[userId, itemId] = (double)recommendTable[userId, itemId] + p;
}
else
{
recommendTable.Add(userId, itemId, p);
}
}
}
}
}
});
return(recommendTable);
}
/// <summary>
/// Mean average precision
/// https://www.kaggle.com/c/coupon-purchase-prediction#evaluation
/// </summary>
/// <param name="recommended">sorted predicted ratings</param>
/// <param name="test">real ratings</param>
/// <returns></returns>
public static double MAP(List <Rating> recommendations, List <Rating> test, int k = 5)
{
Hashtable recommendedRatings = Tools.GetUserItemsTable(recommendations);
MyTable testTable = Tools.GetRatingTable(test); // mark
int validateUserCounter = 0;
double _MAP = 0.0;
foreach (int userId in recommendedRatings.Keys)
{
if (testTable.ContainsMainKey(userId))
{
List <Rating> recommendedUserRatings = (List <Rating>)recommendedRatings[userId];
Hashtable testUserRatings = (Hashtable)testTable[userId];
int length = (k > recommendedUserRatings.Count ? recommendedUserRatings.Count : k);
int[] accuracy = new int[length];
int correctlyPredictedItems = 0;
for (int i = 0; i < length; i++)
{
if (testUserRatings.ContainsKey(recommendedUserRatings[i].ItemId)) // correctly predicted
{
correctlyPredictedItems++;
accuracy[i] = correctlyPredictedItems;
}
}
if (correctlyPredictedItems > 0)
{
double APu = 0.0; // average precision of user u
for (int i = 0; i < length; i++)
{
APu += (accuracy[i] * 1.0 / (i + 1));
}
APu /= length;
_MAP += APu;
}
validateUserCounter++; // recommended users which also in test
}
}
if (validateUserCounter > 0)
{
return(_MAP / validateUserCounter);
}
return(0.0);
}