授業資料/対数尤度比による特徴語抽出

特徴語抽出†

対数尤度比 Log-Likelihood Ratio†

• Excel用の関数(VBA)*1

  Public Function LogLikelihood(ByVal target As Long, comparison As Long, targetTotal As Long, comparisonTotal As Long) As Variant
      a = target
      b = comparison
      c = targetTotal - a
      d = comparisonTotal - b
         
      If a = 0 Then aLNa = 0 Else aLNa = a * LN(a)
      If b = 0 Then bLNb = 0 Else bLNb = b * LN(b)
      
      LNLikelihood = 2 * (aLNa + bLNb + c * LN(c) + d * LN(d) - (a + b) * LN(a + b) - (a + c) * LN(a + c) - (b + d) * LN(b + d) - (c + d) * LN(c + d) + (a + b + c + d) * LN(a + b + c + d))
      
      If target / targetTotal < comparison / comparisonTotal Then LogLikelihood = LogLikelihood * (-1)
     
  End Function

• ダウンロード LLR.xlsm

• cf.『現代日本語書き言葉均衡コーパス』語彙表

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