[理學(xué)]第6講分類和預(yù)測(cè)(編輯修改稿)
2024-11-15 00:54 本頁面
【文章內(nèi)容簡(jiǎn)介】 x c e l l e n t y e s3 1 …4 0 h i g h y e s f a i r y e s 4 0 m e d i u m no e x c e l l e n t no用信息增益計(jì)算進(jìn)行屬性選擇 ? 用 age進(jìn)行劃分 age? overcast =30 40 30..40 age buys_puter =30 no =30 no =30 no =30 yes =30 yes age buys_puter 31?40 yes 31?40 yes 31?40 yes 31?40 yes age buys_puter 40 yes 40 yes 40 no 40 yes 40 no E(age) = 5/14*I(2, 3)+4/14*I(4,0)+5/14*I(3,2) =5/14*(2/5*(log2 (2/5)3/5*(log2 (3/5)) +4/14*(4/4log2 (4/4)0/4log2 (0/4)) +5/14*(3/5log2 (3/5)2/5log2 (2/5)) = Gain(age) = I ( p, n) E (age) = = 用信息增益計(jì)算進(jìn)行屬性選擇 ? 用 ine進(jìn)行劃分 ine? overcast high low m dium E(ine) = 4/14*I(2, 2)+6/14*I(4,2)+4/14*I(3,1) = ine buys_puter high no high no high yes high yes ine buys_puter medium yes medium no medium yes medium yes medium yes medium no ine buys_puter low yes low no low yes low yes Gain(ine) = I ( p, n) E (ine) = = 用信息增益計(jì)算進(jìn)行屬性選擇 ? 用 student進(jìn)行劃分 student? yes no student buys_puter yes Yes yes No yes Yes yes Yes yes Yes yes Yes yes Yes student buys_puter no no no no no yes no yes no no no yes no no E(student) = 7/14*I(6, 1)+7/14*I(3,4) = Gain(student) = I ( p, n) E (student) = = 用信息增益計(jì)算進(jìn)行屬性選擇 ? 用 credit_rating進(jìn)行劃分 credit_rating? excellent fair credit_rating buys_puter Fair no Fair yes Fair yes Fair yes Fair no Fair yes Fair yes fair yes credit_rating buys_puter Excellent no Excellent no Excellent yes Excellent yes Excellent yes excellent no E(credit_rating) = 6/14*I(3, 3)+8/14*I(5,3) = Gain(credit_rating) = I ( p, n) E (credit_rating) = =用信息增益計(jì)算進(jìn)行屬性選擇 Gain(age) = Gain(ine) = Gain(student ) = Gain(credit _ rating ) = age? overcast =30 40 30..40 age buys_puter =30 no =30 no =30 no =30 yes =30 yes age buys_puter 31?40 yes 31?40 yes 31?40 yes 31?40 yes age buys_puter 40 yes 40 yes 40 no 40 yes 40 no age ine student credit_rating class:buys_puter =30 high no fair no =30 high no excellent no =30 medium no fair no =30 low yes fair yes =30 medium yes excellent yes age? overcast student? no yes =30
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