Module: JaroWinkler

Defined in:
lib/jaro_winkler.rb,
lib/jaro_winkler/version.rb,
lib/jaro_winkler/fallback.rb,
ext/jaro_winkler/jaro_winkler.c

Constant Summary collapse

VERSION = 
"1.2.8"

Class Method Summary collapse

Class Method Details

.c_distance ⇒ Object 



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# File 'lib/jaro_winkler.rb', line 60

def r_distance s1, s2, options = {}
  options = {weight: 0.1, threshold: 0.7, ignore_case: false}.merge options
  weight, threshold, ignore_case = options[:weight], options[:threshold], options[:ignore_case]
  raise 'Scaling factor should not exceed 0.25, otherwise the distance can become larger than 1' if weight > 0.25
  s1, s2     = s1.upcase, s2.upcase if ignore_case
  distance   = jaro_distance(s1, s2)
  prefix     = 0
  max_length = [4, s1.length, s2.length].min
  s1[0, max_length].chars.each_with_index do |c1, i|
    c1 == s2[i] ? prefix += 1 : break
  end
  distance < threshold ? distance : distance + ((prefix * weight) * (1 - distance))
end

.distance ⇒ Object 



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# File 'lib/jaro_winkler.rb', line 59

def r_distance s1, s2, options = {}
  options = {weight: 0.1, threshold: 0.7, ignore_case: false}.merge options
  weight, threshold, ignore_case = options[:weight], options[:threshold], options[:ignore_case]
  raise 'Scaling factor should not exceed 0.25, otherwise the distance can become larger than 1' if weight > 0.25
  s1, s2     = s1.upcase, s2.upcase if ignore_case
  distance   = jaro_distance(s1, s2)
  prefix     = 0
  max_length = [4, s1.length, s2.length].min
  s1[0, max_length].chars.each_with_index do |c1, i|
    c1 == s2[i] ? prefix += 1 : break
  end
  distance < threshold ? distance : distance + ((prefix * weight) * (1 - distance))
end

.fallback? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/jaro_winkler/fallback.rb', line 3

def fallback?
  RUBY_PLATFORM == 'java'
end

.jaro_distance(s1, s2) ⇒ Object 



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# File 'lib/jaro_winkler.rb', line 5

def jaro_distance s1, s2
  length1, length2 = s1.length, s2.length
  # Guarantee the length order
  if s1.length > s2.length
    s1, s2 = s2, s1
    length1, length2 = length2, length1
  end
  window_size    = (length2 / 2) - 1
  window_size    = 0 if window_size < 0
  matches        = 0.0
  transpositions = 0
  previous_index = -1
  max_index      = length2 - 1
  s1.chars.each_with_index do |c1, i|
    left      = i - window_size
    right     = i + window_size
    left      = 0         if left  < 0
    right     = max_index if right > max_index
    matched   = false
    found     = false
    s2[left..right].chars.each_with_index do |c2, j|
      if c1 == c2
        matched  = true
        s2_index = left + j
        if !found && s2_index > previous_index
          previous_index = s2_index
          found          = true
        end
      end
    end
    if matched
      matches += 1
      transpositions += 1 unless found
    end
  end
  # Don't divide transpositions by 2 since it's been counted directly by above code.
  matches == 0 ? 0 : (matches / length1 + matches / length2 + (matches - transpositions) / matches) / 3.0
end

.r_distance(s1, s2, options = {}) ⇒ Object 



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# File 'lib/jaro_winkler.rb', line 44

def r_distance s1, s2, options = {}
  options = {weight: 0.1, threshold: 0.7, ignore_case: false}.merge options
  weight, threshold, ignore_case = options[:weight], options[:threshold], options[:ignore_case]
  raise 'Scaling factor should not exceed 0.25, otherwise the distance can become larger than 1' if weight > 0.25
  s1, s2     = s1.upcase, s2.upcase if ignore_case
  distance   = jaro_distance(s1, s2)
  prefix     = 0
  max_length = [4, s1.length, s2.length].min
  s1[0, max_length].chars.each_with_index do |c1, i|
    c1 == s2[i] ? prefix += 1 : break
  end
  distance < threshold ? distance : distance + ((prefix * weight) * (1 - distance))
end