Module: Selector::IG

Included in:
BNS_IG, InformationGain
Defined in:
lib/svm_helper/selectors/calc.rb

Instance Method Summary collapse

Instance Method Details

#e(x, y) ⇒ Object 



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# File 'lib/svm_helper/selectors/calc.rb', line 10

def e(x,y)
  -xlx(x.quo(x+y)) -xlx(y.quo(x+y))
end

#information_gain(pos, neg, tp, fp) ⇒ Object 



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# File 'lib/svm_helper/selectors/calc.rb', line 3

def information_gain(pos, neg, tp, fp)
  fn = neg - fp
  tn = pos - tp
  p_word = (tp + fp).quo(pos + neg)

  e(pos, neg) - (p_word * e(tp, fp) + (1 - p_word) * e(fn, tn))
end

#xlx(x) ⇒ Object 



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# File 'lib/svm_helper/selectors/calc.rb', line 13

def xlx(x)
  x * Math.log2(x)
end