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页数:11页
时间:2019-02-28
《机器学习十大算法:kNN》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、Chapter8kNN:k-NearestNeighborsMichaelSteinbachandPang-NingTanContents8.1Introduction...........................................................1518.2DescriptionoftheAlgorithm...........................................1528.2.1High-LevelDescription.........................................1528.2.
2、2Issues..........................................................1538.2.3SoftwareImplementations......................................1558.3Examples..............................................................1558.4AdvancedTopics.......................................................1578.5Exe
3、rcises..............................................................158Acknowledgments...........................................................159References..................................................................1598.1IntroductionOneofthesimplestandrathertrivialclassifiersistheRotec
4、lassifier,whichmemorizestheentiretrainingdataandperformsclassificationonlyiftheattributesofthetestobjectexactlymatchtheattributesofoneofthetrainingobjects.Anobviousproblemwiththisapproachisthatmanytestrecordswillnotbeclassifiedbecausetheydonotexactlymatchanyofthetrainingrecords.Anotherissuearises
5、whentwoormoretrainingrecordshavethesameattributesbutdifferentclasslabels.Amoresophisticatedapproach,k-nearestneighbor(kNN)classification[10,11,21],findsagroupofkobjectsinthetrainingsetthatareclosesttothetestobject,andbasestheassignmentofalabelonthepredominanceofaparticularclassinthisneighborhood
6、.Thisaddressestheissuethat,inmanydatasets,itisunlikelythatoneobjectwillexactlymatchanother,aswellasthefactthatconflictinginformationabouttheclassofanobjectmaybeprovidedbytheobjectsclosesttoit.Thereareseveralkeyelementsofthisapproach:(i)thesetoflabeledobjectstobeusedforevaluatingatestobject’scla
7、ss,1(ii)adistanceorsimilaritymetricthatcanbeusedtocompute1Thisneednotbetheentiretrainingset.151©2009byTaylor&FrancisGroup,LLC152kNN:k-NearestNeighborstheclosenessofobjects,(iii)thevalueofk,thenumberofnearestneighbors,and(iv)themethoduse
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