Class: Clusterable::Cluster

Inherits:
Object
  • Object
show all
Defined in:
lib/clusterable/cluster.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(points = [], center = nil) ⇒ Cluster

Returns a new instance of Cluster.



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# File 'lib/clusterable/cluster.rb', line 5

def initialize(points = [], center = nil)
  raise "can't initialize an empty cluster" unless points.size > 0
  self.points = points
  self.center = center || calculate_center
end

Instance Attribute Details

#center ⇒ Object

Returns the value of attribute center.



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# File 'lib/clusterable/cluster.rb', line 3

def center
  @center
end

#points ⇒ Object

Returns the value of attribute points.



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# File 'lib/clusterable/cluster.rb', line 3

def points
  @points
end

Class Method Details

.kmeans(points, sample_size, distance_cutoff) ⇒ Object

See: en.wikipedia.org/wiki/K-means_clustering



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# File 'lib/clusterable/cluster.rb', line 12

def self.kmeans(points, sample_size, distance_cutoff)
  initial  = pick_random(points, sample_size)
  clusters = initial.map do |point|
               new([point], point) 
             end
  
  while true
    lists = []
    clusters.each { lists << [] }
    
    points.each do |point|
      smallest_distance = point.distance_to(clusters.first.center)
      index = 0
      
      clusters[1..clusters.length].each.with_index do |cluster, i|
        distance = point.distance_to(cluster.center)
        
        if distance < smallest_distance
          smalles_distance = distance
          index = i + 1
        end
      end
      
      lists[index] << point
    end
    
    biggest_shift = 0.0
    clusters.each.with_index do |cluster, index|
      if lists[index].size > 0
        shift = cluster.update(lists[index])
        biggest_shift = [shift, biggest_shift].max
      end
    end
    
    break if biggest_shift < distance_cutoff
  end
  
  clusters
end

Instance Method Details

#update(points) ⇒ Object 



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# File 'lib/clusterable/cluster.rb', line 52

def update(points)
  self.points = points.compact
  old_center  = center.dup
  self.center = calculate_center
  
  center.distance_to(old_center)
end