Module: Bishop

Defined in:

lib/bishop.rb

Defined Under Namespace

Classes: Bayes, BayesData, Tokenizer

Class Method Summary

• .chi2p(chi, df) ⇒ Object
• .robinson(probs, ignore) ⇒ Object
• .robinson_fisher(probs, ignore) ⇒ Object

Class Method Details

.chi2p(chi, df) ⇒ Object

# File 'lib/bishop.rb', line 307

def self.chi2p( chi, df )
  m = chi / 2
  sum = term = Math.exp( -m )
  (1 .. df/2).each do |i|
    term *= m/i
    sum += term
  end
  [1.0, sum].min
end

.robinson(probs, ignore) ⇒ Object

# File 'lib/bishop.rb', line 281

def self.robinson( probs, ignore )
  nth = 1.0/probs.length
  what_is_p = 1.0 - probs.map { |p| 1.0 - p[1] }.inject( 1.0 ) { |s,v| s * v } ** nth
  what_is_q = 1.0 - probs.map { |p| p[1] }.inject { |s,v| s * v } ** nth
  what_is_s = ( what_is_p - what_is_q ) / ( what_is_p + what_is_q )
  ( 1 + what_is_s ) / 2
end

.robinson_fisher(probs, ignore) ⇒ Object

# File 'lib/bishop.rb', line 289

def self.robinson_fisher( probs, ignore )
  n = probs.length
  
  begin
    h = chi2p( -2.0 * Math.log( probs.map { |p| p[1] }.inject( 1.0 ) { |s,v| s*v } ), 2*n )
  rescue
    h = 0.0
  end

  begin      
    s = chi2p( -2.0 * Math.log( probs.map { |p| 1.0 - p[1] }.inject( 1.0 ) { |s,v| s*v } ), 2*n )
  rescue
    s = 0.0
  end
  
  ( 1 + h - s ) / 2
end