private SingleUserEvaluationResults GetSingleUserEvaluationResults <TInput, TRecommendation>(
IRecommendationSource <TInput, IEnumerable <TRecommendation>, TRecommendation> recSource,
TInput user,
IUserInputClassifier <TInput> goodBadClassifier,
Func <ClassifiedUserInput <TInput>, double, ItemsForInputAndEvaluation <TInput> > inputDivisionFunc,
int numRecsToTryToGet)
where TInput : IInputForUser
where TRecommendation : IRecommendation
{
// Divide into liked and unliked.
// Set aside a random X% of the liked and a random X% of the unliked
ClassifiedUserInput <TInput> classified = goodBadClassifier.Classify(user);
ItemsForInputAndEvaluation <TInput> divided = inputDivisionFunc(classified, FractionOfInputToSetAsideForEvaluation);
// Get top N recommendations
// Keep count of hits and false positives
List <int> recommendedIds = new List <int>();
int truePositivesForThisUser = 0;
int falsePositivesForThisUser = 0;
int unknownsForThisUser = 0;
foreach (TRecommendation recommendation in recSource.GetRecommendations(divided.ItemsForInput, numRecsToTryToGet))
{
recommendedIds.Add(recommendation.ItemId);
if (divided.LikedItemsForEvaluation.Contains(recommendation.ItemId))
{
truePositivesForThisUser++;
}
else if (divided.UnlikedItemsForEvaluation.Contains(recommendation.ItemId))
{
falsePositivesForThisUser++;
}
else
{
unknownsForThisUser++;
}
}
int falseNegativesForThisUser = divided.LikedItemsForEvaluation.Count - truePositivesForThisUser;
SingleUserEvaluationResults results = new SingleUserEvaluationResults()
{
TruePositives = truePositivesForThisUser,
FalsePositives = falsePositivesForThisUser,
Unknowns = unknownsForThisUser,
FalseNegatives = falseNegativesForThisUser,
};
return(results);
}
/// <summary>
///
/// </summary>
/// <typeparam name="TInput"></typeparam>
/// <typeparam name="TRecommendation"></typeparam>
/// <param name="recSource">A recommendation source that has already been trained.</param>
/// <param name="users">The users to use in evaluation by getting recommendations for them.</param>
/// <param name="goodBadClassifier">Classifier to classify input for a user into liked items and unliked items. If an
/// item was left out of the input passed to the recommendation source and it gets recommended, this determines whether
/// it gets considered a true positive or a false positive.</param>
/// <param name="inputDivisionFunc">Takes a user's classified input and a fraction to set aside (.2 for 20%) and returns
/// a new user input object and the items that were set aside.</param>
/// <param name="numRecsToTryToGet">Number of recommendations to try to get for each user.</param>
/// <returns></returns>
public EvaluationResults Evaluate <TInput, TRecommendation>(
IRecommendationSource <TInput, IEnumerable <TRecommendation>, TRecommendation> recSource,
ICollection <TInput> users,
IUserInputClassifier <TInput> goodBadClassifier,
Func <ClassifiedUserInput <TInput>, double, ItemsForInputAndEvaluation <TInput> > inputDivisionFunc,
int numRecsToTryToGet)
where TInput : IInputForUser
where TRecommendation : IRecommendation
{
EvaluationResults results = new EvaluationResults()
{
TotalTruePositives = 0,
TotalFalsePositives = 0,
TotalUnknown = 0,
TotalFalseNegatives = 0,
TotalPrecision = 0,
NumPrecision = 0,
TotalRecall = 0,
NumRecall = 0
};
foreach (TInput user in users)
{
SingleUserEvaluationResults userResults = GetSingleUserEvaluationResults(recSource, user, goodBadClassifier,
inputDivisionFunc, numRecsToTryToGet);
results.TotalTruePositives += userResults.TruePositives;
results.TotalFalsePositives += userResults.FalsePositives;
results.TotalUnknown += userResults.Unknowns;
results.TotalFalseNegatives += userResults.FalseNegatives;
if (userResults.Precision.HasValue)
{
results.TotalPrecision += userResults.Precision.Value;
results.NumPrecision++;
}
if (userResults.Recall.HasValue)
{
results.TotalRecall += userResults.Recall.Value;
results.NumRecall++;
}
}
return(results);
}
