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Contents
module DbClustering
module DistanceMetrics
class CosineSimilarity
include Math
def initialize(min_dimensions: 1)
@min_dimensions = min_dimensions
end
def distance(vector1, vector2)
1.0 - correlation(vector1, vector2)
end
def correlation(vector1, vector2)
vector1_array = vector1.array_for_comparison(vector2)
vector2_array = vector2.array_for_comparison(vector1)
if vector1_array.count != vector2_array.count
raise "Vectors with different sizes cannot be compared"
end
if vector1_array.count < @min_dimensions
return Float::INFINITY
end
# see here for calculation formula: https://en.wikipedia.org/wiki/Cosine_similarity
numerator = 0
vector1_array.count.times do |i|
numerator += vector1_array[i] * vector2_array[i]
end
left_sqrt = sqrt(vector1_array.reduce(0) { |sum, v1i| sum + v1i ** 2 })
right_sqrt = sqrt(vector2_array.reduce(0) { |sum, v2i| sum + v2i ** 2 })
denominator = left_sqrt * right_sqrt
numerator.to_f / denominator
end
end
end
end
Version data entries
17 entries across 17 versions & 1 rubygems