public static double CosineScore(SuggestorUser user, SuggestorUser otherUser)
{
// TF-IDF
Dictionary<string, SuggestorCollectionLine> mutualLines = new Dictionary<string, SuggestorCollectionLine>();
mutualLines = user.CollectionLines.Keys.Intersect(otherUser.CollectionLines.Keys).ToDictionary(t => t, t => user.CollectionLines[t]);
double cosScore = 0;
double termProductSum = 0;
foreach (string lineId in mutualLines.Keys)
{
termProductSum += user.CollectionLines[lineId].Weight * otherUser.CollectionLines[lineId].Weight;
}
double vectorNormalizingMultiplication = (GetSize(user) * GetSize(otherUser));
if (vectorNormalizingMultiplication == 0)
return 0;
cosScore = termProductSum / vectorNormalizingMultiplication;
return cosScore;
}
/*
private Dictionary<SuggestorCollection, double> FindClosestInvoices(Dictionary<string, SuggestorCollection> collections, SuggestorCollection compareCollection, int n)
{
// TODO: Disgusting code
Dictionary<SuggestorCollection, double> topInvoices = new Dictionary<SuggestorCollection, double>();
List<SuggestorCollection> compareInvoices = collections.Values.ToList();
compareInvoices.Remove(compareCollection);
// Calculate all weights
// TODO: Cache this. Per instance?
foreach (SuggestorCollection invoice in compareInvoices)
{
topInvoices.Add(invoice, SuggestorCollectionFunctions.CosineScore(invoice, compareCollection));
}
List<KeyValuePair<SuggestorCollection, double>> topValues = topInvoices.ToList();
topValues.Sort((firstPair, nextPair) => { return firstPair.Value.CompareTo(nextPair.Value); });
topValues.Reverse();
Dictionary<SuggestorCollection, double> returnInvoices = new Dictionary<SuggestorCollection, double>();
for (int i = 0; i < n; i++)
{
if (topValues[i].Value != 0)
returnInvoices.Add(topValues[i].Key, topValues[i].Value);
}
return returnInvoices;
}
public Dictionary<string, double> GetRecommendedItems(SuggestorCollection compareInvoice)
{
if (compareInvoice.GetCollectionLines().Count == 0) return null;
Dictionary<string, double> itemAggregation = new Dictionary<string, double>();
Dictionary<SuggestorCollection, double> topInvoices = FindClosestInvoices(compareInvoice, 10);
foreach (SuggestorCollection invoice in topInvoices.Keys)
{
foreach (string itemNo in invoice.GetCollectionLines().Keys)
{
if (compareInvoice.GetCollectionLines().ContainsKey(itemNo)) continue; // Ignore items that are already in basket
if (!(itemAggregation.ContainsKey(itemNo))) itemAggregation.Add(itemNo, 1);
itemAggregation[itemNo]++;
//itemAggregation[itemNo] += topInvoices[invoice] * 1.0;
}
}
List<KeyValuePair<string, double>> itemAggregationList = itemAggregation.ToList();
// Sort dictionary by value
itemAggregationList.Sort((firstPair, nextPair) => { return firstPair.Value.CompareTo(nextPair.Value); });
itemAggregationList.Reverse();
itemAggregation = itemAggregationList.ToDictionary(pair => pair.Key, pair => pair.Value);
return itemAggregation;
}*/
public override Dictionary<SuggestorUser, double> SuggestNUsers(List<SuggestorUser> users, SuggestorUser user, int n)
{
throw new NotImplementedException();
}
public Dictionary<SuggestorUser, double> SuggestUsers(List<SuggestorUser> usersToCompareTo, SuggestorUser user, int n)
{
return recommenderEngine.SuggestNUsers(usersToCompareTo, user, n);
}
public override Dictionary<SuggestorUser, double> SuggestNUsers(List<SuggestorUser> users, SuggestorUser compareUser, int n)
{
// TODO: Disgusting code
Dictionary<SuggestorUser, double> topUsers = new Dictionary<SuggestorUser, double>();
List<SuggestorUser> compareUsers = users.ToList();
compareUsers.Remove(compareUser);
// TODO: Cache this. Per instance?
foreach (SuggestorUser user in compareUsers)
{
// Find cosine similarity between users lines and other users lines
topUsers.Add(user, SuggestorCollectionFunctions.CosineScore(user, compareUser));
}
List<KeyValuePair<SuggestorUser, double>> topValues = topUsers.ToList();
topValues.Sort((firstPair, nextPair) => { return firstPair.Value.CompareTo(nextPair.Value); });
topValues.Reverse();
Dictionary<SuggestorUser, double> returnUsers = new Dictionary<SuggestorUser, double>();
foreach (KeyValuePair<SuggestorUser, double> pair in topValues.Take(n))
{
//if (topValues[i].Value != 0)
//returnUsers.Add(topValues[i].Key, topValues[i].Value);
returnUsers.Add(pair.Key, pair.Value);
}
return returnUsers;
}
public static double GetSize(SuggestorUser user)
{
double squaredSum = 0;
foreach (SuggestorCollectionLine line in user.CollectionLines.Values)
{
squaredSum += Math.Pow(line.Weight, 2);
}
return Math.Sqrt(squaredSum);
}
public abstract Dictionary<SuggestorUser, double> SuggestNUsers(List<SuggestorUser> users, SuggestorUser user, int n);
