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1、PredictiveAnalyticsandMachineLearningPredictiveanalyticsandmachinelearningarehot,newresearchfields.Theyarenewcomparedtootherfieldsand,withoutadoubt,wecanexpectalotofrapidgrowth.Itisevenpredictedthatmachinelearningwillacceleratesofastthatwithinmeredecadeshumanlaborwillbereplacedbyintelligentmac
2、hines(seehttp://en.wikipedia.org/wiki/Technological_singularity).Thecurrentstateofartisfarfromthatutopia.Alotofcomputingpoweranddataisstillneededtomakeevensimpledecisions,suchasdeterminingwhetherpicturesontheInternetcontaindogsorcats.Predictiveanalyticsusesavarietyoftechniques,includingmachine
3、learningtomakeusefulpredictions,forinstance,todeterminewhetheracustomercanrepayhisorherloansoridentifyfemalecustomerswhoarepregnant(seehttp://www.forbes.com/sites/kashmirhill/2012/02/16/how-target-figured-out-a-teen-girl-was-pregnant-before-her-father-did/).Tomakethesepredictions,featuresareex
4、tractedfromhugevolumesofdata.Wementionedfeaturesbefore—theyarealsocalledpredictors.Featuresareinputvariablesthatcanbeusedtomakepredictions.Inessence,wehavefeaturesfoundinourdataandwearelookingforafunctionthatmapsthefeaturestoatarget,whichmayormaynotbeknown.Findingtheappropriatefunctioncanbehar
5、d;often,differentalgorithmsandmodelsaregroupedtogetherinsocalledensembles.Theoutputofanensemblecanbeamajorityvoteoranaverageofagroupofmodels,butwecanalsouseamoreadvancedalgorithmtoproducethefinalresult.Wewillnotbeusingensemblesinthischapter,butitissomethingtokeepinmind.PredictiveAnalyticsandMa
6、chineLearningInthepreviouschapter,wegotatasteofmachinelearningalgorithms—theNaiveBayesclassificationalgorithm.Wecandividemachinelearningintothefollowingcategories:•Supervisedlearning:Thisrequiresustolabeltrainingdata.Forinstance,ifwewanttoclassifyspam,weneedtoprovideexamplesofspamandnormale-ma
7、ilmessages.•Unsupervisedlearning:Thisdoesn'trequirehumaninput.Thistypeoflearningcandiscoverpatternssuchasclustersinlargedatasets.•Reinforcementlearning:Thisislearningwithoutatutor,butwithsomesortoffeedback.Forexample,acomputercanplayche
