private UsersSimilarity ComputeSimilarityBetweenUsers(int userId, int comparedUserId,
DistanceSimilarityEnum similarityDistance)
{
var similarity = _usersSelector.SelectMutualAndUniqueBooksForUsers(userId, comparedUserId);
if (similarity == null)
{
return(null);
}
switch (similarityDistance)
{
case DistanceSimilarityEnum.CosineSimilarity:
similarity.Similarity = GetCosineDistance(similarity.UserRatesForMutualBooks,
similarity.ComparedUserRatesForMutualBooks);
break;
case DistanceSimilarityEnum.PearsonSimilarity:
similarity.Similarity =
GetPearsonCorrelationSimilarity(similarity.UserRatesForMutualBooks,
similarity.ComparedUserRatesForMutualBooks);
break;
default:
throw new ArgumentOutOfRangeException();
}
similarity.SimilarityType = (int)similarityDistance;
return(similarity);
}
public void GetNearestNeighbors_WhenBookRatesAreDifferent_ShouldReturnMinSimilarity(
DistanceSimilarityEnum distance, double expected)
{
_settings.SimilarityDistance = distance;
var similarity = new UsersSimilarity
{
ComparedUserRatesForMutualBooks = _helpers.CreateBookScores(2, new[] { "1", "2", "3" }, new short[] { 1, 1, 1 }),
UserRatesForMutualBooks = _helpers.CreateBookScores(2, new[] { "1", "2", "3" }, new short[] { 10, 10, 10 }),
};
_usersSelector.SelectMutualAndUniqueBooksForUsers(1, 2).Returns(similarity);
var actual = _sut.GetNearestNeighbors(1, new List <int>()
{
2
}, _settings).FirstOrDefault();
actual.ShouldNotBeNull();
actual.Similarity.Value.ShouldBe(expected, 2);
}
public void GetNearestNeighbors_ShouldReturnTwoMostSimilarUsers(DistanceSimilarityEnum distance)
{
_settings.SimilarityDistance = distance;
var similarity_1 = new UsersSimilarity
{
ComparedUserRatesForMutualBooks = _helpers.CreateBookScores(2, new[] { "1", "2", "3" }, new short[] { 1, 2, 2 }),
UserRatesForMutualBooks = _helpers.CreateBookScores(1, new[] { "1", "2", "3" }, new short[] { 1, 2, 2 }),
ComparedUserId = 2
};
var similarity_2 = new UsersSimilarity
{
ComparedUserRatesForMutualBooks = _helpers.CreateBookScores(3, new[] { "1", "2", "3" }, new short[] { 1, 2, 2 }),
UserRatesForMutualBooks = _helpers.CreateBookScores(1, new[] { "1", "2", "3" }, new short[] { 1, 4, 2 }),
ComparedUserId = 3
};
var similarity_3 = new UsersSimilarity
{
ComparedUserRatesForMutualBooks = _helpers.CreateBookScores(4, new[] { "1", "2", "3" }, new short[] { 1, 2, 2 }),
UserRatesForMutualBooks = _helpers.CreateBookScores(1, new[] { "1", "2", "3" }, new short[] { 10, 5, 3 }),
ComparedUserId = 4
};
_usersSelector.SelectMutualAndUniqueBooksForUsers(1, 2).Returns(similarity_1);
_usersSelector.SelectMutualAndUniqueBooksForUsers(1, 3).Returns(similarity_2);
_usersSelector.SelectMutualAndUniqueBooksForUsers(1, 4).Returns(similarity_3);
var actual = _sut.GetNearestNeighbors(1, new List <int>()
{
2, 3, 4
}, _settings);
actual.ShouldNotBeNull();
actual.Select(x => x.ComparedUserId).ShouldBe(new[] { 2, 3 });
actual.Count.ShouldBe(2);
}