Class: Suggestor::Algorithms::EuclideanDistance

Inherits:
Object
  • Object
show all
Includes:
RecommendationAlgorithm
Defined in:
lib/suggestor/algorithms/euclidean_distance.rb

Overview

The closest they are, the more similar their tastes are. More info at: 

http://en.wikipedia.org/wiki/Euclidean_metric
http://en.wikipedia.org/wiki/Distance_correlation

Instance Attribute Summary

Attributes included from RecommendationAlgorithm

#collection

Instance Method Summary collapse

Methods included from RecommendationAlgorithm

#initialize, #no_shared_items_between?, #recommented_related_items_for, #shared_items_between, #similar_items_to

Instance Method Details

#inverse_of_sum_of_squares_between(first, second) ⇒ Object 



32
33
34
 
# File 'lib/suggestor/algorithms/euclidean_distance.rb', line 32

def inverse_of_sum_of_squares_between(first, second)
  1/(1+sum_squares_of_shared_items_between(first, second))
end

#similarity_score_between(first, second) ⇒ Object 



27
28
29
30
 
# File 'lib/suggestor/algorithms/euclidean_distance.rb', line 27

def similarity_score_between(first, second)
  return 0.0 if no_shared_items_between?(first, second)
  inverse_of_sum_of_squares_between(first, second)
end

#sum_squares_of_shared_items_between(first, second) ⇒ Object 



36
37
38
39
40
 
# File 'lib/suggestor/algorithms/euclidean_distance.rb', line 36

def sum_squares_of_shared_items_between(first, second)
  shared_items_between(first, second).inject(0.0) do |sum, item|
    sum + (values_for(first)[item] - values_for(second)[item])**2
  end
end