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《8）20161007 Classification Probabilistic Generative Model》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。
1、Classification:ProbabilisticGenerativeModelClassification?FunctionClassn•CreditScoring•Input:income,savings,profession,age,pastfinancialhistory……•Output:acceptorrefuse•MedicalDiagnosis•Input:currentsymptoms,age,gender,pastmedicalhistory……•Output:whichkindofdiseases•Handwritten
2、characterrecognitionoutput:Input:金•Facerecognition•Input:imageofaface,output:personExampleApplication?=?=?=pokemongames(NOTpokemoncardsorPokemonGo)ExampleApplication•Total:sumofallstatsthatcomeafterthis,ageneralguidetohowstrongapokemonis320•HP:hitpoints,orhealth,defineshowmuch
3、damageapokemoncanwithstandbeforefainting35•Attack:thebasemodifierfornormalattacks(eg.Scratch,Punch)55•Defense:thebasedamageresistanceagainstnormalattacks•SPAtk:specialattack,thebasemodifierforspecialattacks(e.g.fire40blast,bubblebeam)•SPDef:thebasedamageresistanceagainstspecia
4、lattacks5050•Speed:determineswhichpokemonattacksfirsteachround90Canwepredictthe“type”ofpokemonbasedontheinformation?ExampleApplicationHowtodoClassification•TrainingdataforClassification?1,?ො1?2,?ො2……??,?ො?ClassificationasRegression?BinaryclassificationasexampleTraining:Class1m
5、eansthetargetis1;Class2meansthetargetis-1Testing:closerto1→class1;closerto-1→class2b+wx+wx=0todecreaseerror1111Class2Class2-1-111x2x2Class1Class1>>1y=b+wx+wxerror1122xx11Penalizetotheexamplesthatare“toocorrect”…(Bishop,P186)•Multipleclass:Class1meansthetargetis1;Class2meansthe
6、targetis2;Class3meansthetargetis3……problematicIdealAlternatives??•Function(Model):??>0Output=class1?????Output=class2•Lossfunction:Thenumberoftimesf??=????≠?ො?getincorrectresultson?trainingdata.•Findthebestfunction:•Example:Perceptron,SVMNotTodayTwoBoxesBox1Box2P(B1)=2/3P(B2)
7、=1/3P(Blue
8、B1)=4/5P(Blue
9、B1)=2/5P(Green
10、B1)=1/5P(Green
11、B1)=3/5fromoneoftheboxesWheredoesitcomefrom??Blue
12、?1??1P(B
13、Blue)=1?Blue
14、?1??1+?Blue
15、?2??2EstimatingtheProbabilitiesTwoClassesFromtrainingdataClass1Class2P(C1)P(C2)P(x
16、C1)P(x
17、C2)Givenanx,whichclassdoesitbelongto??
18、?1??1??1
19、
20、?=??
21、?1??1+??
22、?2??2GenerativeModel??=??
23、?1??1+??
24、?2??2PriorCl
