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);
}