Class: LSA

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(matrix) ⇒ LSA

Returns a new instance of LSA.



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# File 'lib/lsa.rb', line 6

def initialize(matrix)
  @u, @s, @v = matrix.decompose(2)
end

Instance Attribute Details

#s ⇒ Object

Returns the value of attribute s.



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# File 'lib/lsa.rb', line 4

def s
  @s
end

#u ⇒ Object

Returns the value of attribute u.



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# File 'lib/lsa.rb', line 4

def u
  @u
end

#v ⇒ Object

Returns the value of attribute v.



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# File 'lib/lsa.rb', line 4

def v
  @v
end

Instance Method Details

#classify_vector(values) ⇒ Object

Return a distance (cosine similarity) between a new vector, and all the clusters (columns) used in the original matrix. Returns a sorted list of indexes and distances,



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# File 'lib/lsa.rb', line 17

def classify_vector(values)
  raise "Unsupported vector length" unless values.size == @u.row_size || values.size == @v.row_size
  vector = Matrix.row_vector(values)
  mult_matrix = (values.size == @u.row_size ? @u : @v)
  comp_matrix = (values.size == @u.row_size ? @v : @u)
  
  position = vector * mult_matrix * @s.inverse
  x = position[0,0]
  y = position[0,1]
  results = []
  
  comp_matrix.row_size.times do |index|
    results << [index, cosine_similarity(x, y, comp_matrix[index, 0], comp_matrix[index, 1])]
  end
  
  results.sort {|a, b| b[1] <=> a[1]}
end

#cosine_similarity(x1, y1, x2, y2) ⇒ Object

Determines the cosine similarity between two 2D points



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# File 'lib/lsa.rb', line 36

def cosine_similarity(x1, y1, x2, y2)
  dp = (x1 * x2) + (y1 * y2)
  mag1 = Math.sqrt((x1 ** 2) + (y1 ** 2))
  mag2 = Math.sqrt((x2 ** 2) + (y2 ** 2))
  return 0 if mag1 == 0 || mag2 == 0
  return (dp / (mag1 * mag2))
end

#inspect ⇒ Object 



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# File 'lib/lsa.rb', line 10

def inspect
  "U:\n#{@u.inspect}\n\nS:\n#{@s.inspect}\n\nV:\n#{@v.inspect}"
end