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Smoothing Problem with MLE BeijingShanghai…MengChengCLASS = ‘china’ 11…0+ 10…0+ 01…0+ 00…0- A small city in the Anhui province BeijingShanghai…MengChengCLASS.

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Presentation on theme: "Smoothing Problem with MLE BeijingShanghai…MengChengCLASS = ‘china’ 11…0+ 10…0+ 01…0+ 00…0- A small city in the Anhui province BeijingShanghai…MengChengCLASS."— Presentation transcript:

1 Smoothing Problem with MLE BeijingShanghai…MengChengCLASS = ‘china’ 11…0+ 10…0+ 01…0+ 00…0- A small city in the Anhui province BeijingShanghai…MengChengCLASS = ‘china’ 11…1? Common reasons: data sparseness, rare features, …

2 Smoothing Add-one smoothing (Laplace smoothing) –Essentially, every possible value for a variable have non-zero count in any class BeijingShanghai…MengChengCLASS = ‘china’ 11…0+ B = # of possible values for the variable in question.

3 Bernoulli Training Chinese Beijing Chinese+ Chinese Chinese Shanghai+ Chinese Macao+ Tokyo Japan Chinese- ChineseBeijingShanghaiMacaoTokyoJapanCLASS

4 Bernoulli Training ChineseBeijingShanghaiMacaoTokyoJapanCLASS ChineseBeijingShanghaiMacaoTokyoJapanCLASS * * 1 B = # of possible values for the variable in question = 2

5 Bernoulli Testing Chinese Chinese Chinese Tokyo Japan? ChineseBeijingShanghaiMacaoTokyoJapanCLASS * * 1 ChineseBeijingShanghaiMacaoTokyoJapanCLASS ?

6 Multinomial Training Chinese Beijing Chinese+ Chinese Chinese Shanghai+ Chinese Macao+ Tokyo Japan Chinese- W1W2W3WiCLASS ChineseBeijingChinese+ Shanghai+ ChineseMacao+ TokyoJapanChinese-

7 Multinomial Training W1W2W3CLASS ChineseBeijingChinese+ Shanghai+ ChineseMacao+ TokyoJapanChinese- WiCLASS Chinese+ Beijing+ Chinese+ + + Shanghai+ Chinese+ Macao+ Tokyo- Japan- Chinese- B = # of possible values for the variable in question = 6

8 Multinomial Testing Chinese Chinese Chinese Tokyo Japan? W1W2W3W4W5CLASS Chinese TokyoJapan? WCLASS Chinese+ Beijing+ Chinese+ + + Shanghai+ Chinese+ Macao+ Tokyo- Japan- Chinese-


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