public double predictRating(BookUser user, BookItem item)
{
switch (type)
{
case RecommendationType.USER_BASED:
return(estimateUserBasedRating(user, item));
case RecommendationType.IMPROVED_USER_BASED:
return(estimateUserBasedRating(user, item));
case RecommendationType.ITEM_BASED:
return(estimateItemBasedRating(user, item));
case RecommendationType.ITEM_PENALTY_BASED:
return(estimateItemBasedRating(user, item));
case RecommendationType.USER_CONTENT_BASED:
throw new Exception("Not valid for current similarity type:" + type);
case RecommendationType.USER_ITEM_CONTENT_BASED:
return(MAX_RATING * similarityMatrix.getValue(user.UserId, item.getId()));
default:
throw new Exception("Unknown recommendation type:" + type);
}
}
public double getSimilarity(BookItem i1, BookItem i2)
{
double sim = similarityMatrix.getValue(i1.getId(), i2.getId());
// verbose - флаг, отвечающий за пояснение всего (многословный дословно)
if (verbose)
{
Console.WriteLine("Item similarity between");
Console.WriteLine(" ItemID: " + i1.getId());
Console.WriteLine(" and");
Console.WriteLine(" ItemID: " + i2.getId());
Console.WriteLine(" is equal to " + sim);
}
return(sim);
}
private double estimateItemBasedRating(BookUser user, BookItem item)
{
double estimatedRating = item.getAverageRating();
int itemId = item.getId();
int userId = user.UserId;
double similaritySum = 0.0;
double weightedRatingSum = 0.0;
GeneralRating existingRatingByUser = user.getItemRating(item.getId());
if (existingRatingByUser != null)
{
estimatedRating = existingRatingByUser.getRating();
}
else
{
double similarityBetweenItems = 0;
double weightedRating = 0;
dataSet.getBooks().ForEach(delegate(BookItem anotherItem) {
// Рассматриваются только те элементы, которые оценивал пользователь
GeneralRating anotherItemRating = anotherItem.getUserRating(userId);
if (anotherItemRating != null)
{
similarityBetweenItems = similarityMatrix.getValue(itemId, anotherItem.getId());
if (similarityBetweenItems > similarityThreshold)
{
weightedRating = similarityBetweenItems * anotherItemRating.getRating();
weightedRatingSum += weightedRating;
similaritySum += similarityBetweenItems;
}
}
});
if (similaritySum > 0.0)
{
estimatedRating = weightedRatingSum / similaritySum;
}
}
return(estimatedRating);
}
//--------------------------------------------------------------------
// Приватные вспомогательные методы
//--------------------------------------------------------------------
private double estimateUserBasedRating(BookUser user, BookItem item)
{
double estimatedRating = user.getAverageRating();
int itemId = item.getId();
int userId = user.UserId;
double similaritySum = 0.0;
double weightedRatingSum = 0.0;
// Проверка, оценивал ли пользователь этот элемент
GeneralRating existingRatingByUser = user.getItemRating(item.getId());
if (existingRatingByUser != null)
{
estimatedRating = existingRatingByUser.getRating();
}
else
{
dataSet.getUsers().ForEach(delegate(BookUser anotherUser){
GeneralRating itemRating = anotherUser.getItemRating(itemId);
if (itemRating != null)
{
double similarityBetweenUsers = similarityMatrix.getValue(userId, anotherUser.UserId);
double ratingByNeighbor = itemRating.getRating();
double weightedRating = similarityBetweenUsers * ratingByNeighbor;
weightedRatingSum += weightedRating;
similaritySum += similarityBetweenUsers;
}
});
if (similaritySum > 0.0)
{
estimatedRating = weightedRatingSum / similaritySum;
}
}
return(estimatedRating);
}
private bool skipItem(BookUser user, BookItem item)
{
bool skipItem = true;
//if (isContentBased()) {
// if (user.getUserContent(item.getItemContent().getId()) ==null){
// skipItem = false;
// }
//}
if (user.getItemRating(item.getId()) == null)
{
skipItem = false;
}
return(skipItem);
}
