/// <summary>
/// Finds related items for every item in a given instance source.
/// The subset of items which will be returned as related for a particular item is restricted:
/// it is guaranteed that all the related items have been rated by at least <paramref name="minCommonRatingCount"/> users in common with the query item
/// in the dataset.
/// </summary>
/// <typeparam name="TFeatureSource">The type of a feature source used by the recommendation engine.</typeparam>
/// <param name="recommender">The recommendation engine.</param>
/// <param name="instanceSource">The instance source.</param>
/// <param name="maxRelatedItemCount">Maximum number of related items to return.</param>
/// <param name="minCommonRatingCount">Minimum number of users that the query item and the related item should have been rated by in common.</param>
/// <param name="minRelatedItemPoolSize">
/// If an item has less than <paramref name="minRelatedItemPoolSize"/> possible related items,
/// it will be skipped.
/// </param>
/// <param name="featureSource">The source of features.</param>
/// <returns>The list of related items for every item in <paramref name="instanceSource"/>.</returns>
public IDictionary <TItem, IEnumerable <TItem> > FindRelatedItemsRatedBySameUsers <TFeatureSource>(
IRecommender <TInstanceSource, TUser, TItem, TPredictedRating, TPredictedRatingDist, TFeatureSource> recommender,
TInstanceSource instanceSource,
int maxRelatedItemCount,
int minCommonRatingCount,
int minRelatedItemPoolSize,
TFeatureSource featureSource = default(TFeatureSource))
{
if (recommender == null)
{
throw new ArgumentNullException("recommender");
}
if (maxRelatedItemCount <= 0)
{
throw new ArgumentOutOfRangeException("maxRelatedItemCount", "The maximum number of related items should be positive.");
}
if (minCommonRatingCount <= 0)
{
throw new ArgumentOutOfRangeException("minCommonRatingCount", "The minimum number of common ratings should be positive.");
}
if (minRelatedItemPoolSize <= 0)
{
throw new ArgumentOutOfRangeException("minRelatedItemPoolSize", "The minimum size of the related items pool should be positive.");
}
return(FindRelatedEntitiesWhichRatedTheSame(
this.mapping.GetItems(instanceSource),
item => this.mapping.GetItemsRatedBySameUsers(instanceSource, item),
(item, itemSubset) =>
{
recommender.ItemSubset = itemSubset;
return recommender.GetRelatedItems(item, maxRelatedItemCount, featureSource);
},
minCommonRatingCount,
minRelatedItemPoolSize));
}
