public void testNumUsersPreferring()
{
Assert.AreEqual(2, model.GetNumUsersWithPreferenceFor(456));
Assert.AreEqual(0, model.GetNumUsersWithPreferenceFor(111));
Assert.AreEqual(0, model.GetNumUsersWithPreferenceFor(111, 456));
Assert.AreEqual(2, model.GetNumUsersWithPreferenceFor(123, 234));
}
public override double ItemSimilarity(long itemID1, long itemID2)
{
IDataModel dataModel = getDataModel();
int preferring1 = dataModel.GetNumUsersWithPreferenceFor(itemID1);
int preferring2 = dataModel.GetNumUsersWithPreferenceFor(itemID2);
int intersection = dataModel.GetNumUsersWithPreferenceFor(itemID1, itemID2);
return(doSimilarity(preferring1, preferring2, intersection));
}
private double doItemSimilarity(long itemID1, long itemID2, int preferring1)
{
IDataModel dataModel = getDataModel();
int preferring1and2 = dataModel.GetNumUsersWithPreferenceFor(itemID1, itemID2);
if (preferring1and2 == 0)
{
return(Double.NaN);
}
int preferring2 = dataModel.GetNumUsersWithPreferenceFor(itemID2);
return((double)preferring1and2 / (double)(preferring1 + preferring2 - preferring1and2));
}
public override double[] ItemSimilarities(long itemID1, long[] itemID2s)
{
IDataModel dataModel = getDataModel();
int preferring1 = dataModel.GetNumUsersWithPreferenceFor(itemID1);
double[] distance = new double[itemID2s.Length];
for (int i = 0; i < itemID2s.Length; ++i)
{
int preferring2 = dataModel.GetNumUsersWithPreferenceFor(itemID2s[i]);
int intersection = dataModel.GetNumUsersWithPreferenceFor(itemID1, itemID2s[i]);
distance[i] = doSimilarity(preferring1, preferring2, intersection);
}
return(distance);
}
public override double ItemSimilarity(long itemID1, long itemID2)
{
IDataModel dataModel = getDataModel();
long preferring1 = dataModel.GetNumUsersWithPreferenceFor(itemID1);
long numUsers = dataModel.GetNumUsers();
return(doItemSimilarity(itemID1, itemID2, preferring1, numUsers));
}
private double doItemSimilarity(long itemID1, long itemID2, long preferring1, long numUsers)
{
IDataModel dataModel = getDataModel();
long preferring1and2 = dataModel.GetNumUsersWithPreferenceFor(itemID1, itemID2);
if (preferring1and2 == 0)
{
return(Double.NaN);
}
long preferring2 = dataModel.GetNumUsersWithPreferenceFor(itemID2);
double logLikelihood =
LogLikelihood.logLikelihoodRatio(preferring1and2,
preferring2 - preferring1and2,
preferring1 - preferring1and2,
numUsers - preferring1 - preferring2 + preferring1and2);
return(1.0 - 1.0 / (1.0 + logLikelihood));
}
public virtual int GetNumUsersWithPreferenceFor(long itemID)
{
if (tempPrefs == null)
{
return(_delegate.GetNumUsersWithPreferenceFor(itemID));
}
bool found = false;
for (int i = 0; i < tempPrefs.Length(); i++)
{
if (tempPrefs.GetItemID(i) == itemID)
{
found = true;
break;
}
}
return(_delegate.GetNumUsersWithPreferenceFor(itemID) + (found ? 1 : 0));
}
public override double[] ItemSimilarities(long itemID1, long[] itemID2s)
{
IDataModel dataModel = getDataModel();
long preferring1 = dataModel.GetNumUsersWithPreferenceFor(itemID1);
long numUsers = dataModel.GetNumUsers();
int length = itemID2s.Length;
double[] result = new double[length];
for (int i = 0; i < length; i++)
{
result[i] = doItemSimilarity(itemID1, itemID2s[i], preferring1, numUsers);
}
return(result);
}
public override int GetNumUsersWithPreferenceFor(long itemID)
{
return(_delegate.GetNumUsersWithPreferenceFor(itemID));
}
