140
CS 6140: Machine Learning Spring 2017 Instructor: Lu Wang College of Computer and Informa@on Science Northeastern University Webpage: www.ccs.neu.edu/home/luwang Email: [email protected]

CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

  • Upload
    lequynh

  • View
    218

  • Download
    0

Embed Size (px)

Citation preview

Page 1: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

CS6140:MachineLearningSpring2017

Instructor:LuWangCollegeofComputerandInforma@onScience

NortheasternUniversityWebpage:www.ccs.neu.edu/home/luwang

Email:[email protected]

Page 2: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Logis@cs

•  Assignment1isout– Due2/9/2017– Startearly!

Page 3: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Whatwelearnedlast@me

•  Evalua@onmetrics

•  DecisionTree

•  Genera@veModels

•  Genera@veModelandDiscrimina@veModel

•  Logis@cRegression

Page 4: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 5: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 6: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 7: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

ROCPlot

•  Sensi@vity=a/(a+b)=Recall– Trueposi@verate

•  1-Specificity=1-d/(c+d)=c/(c+d)– Falseposi@verate

Page 8: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 9: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

DecisionTree

•  Playtennis?

•  Eachinternalnode:testonefeatureXi•  Eachbranchfromanode:selectsonevalueforXi•  Eachleafnode:predictY(orP(Y|X∈leaf))

Page 10: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Top-DownInduc@onofDecisionTrees

•  Whicha_ributetouseforsplit?

Page 11: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Top-DownInduc@onofDecisionTrees

•  Whicha_ributetouseforsplit?•  Goodsplitifwearemorecertainaboutclassifica@ona`ersplit– Determinis@cgood(alltrueorallfalse)– Uniformdistribu@onbad– Whataboutdistribu@oninbetween?

Page 12: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Informa@onGain

•  Gain(S,A)=expectedreduc@oninentropyduetosor@ngonA

Page 13: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Informa@onGain

Page 14: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Overficng

Page 15: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 16: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Bayesianmodel

•  H:Hypothesisspaceofpossibleconcepts•  X:nexamplesofaconceptC•  EvaluatehypothesesgivendatausingBayes’rule:

Page 17: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

NaïveBayes

Page 18: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

MaximumLikelihoodEs@ma@on

Page 19: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

MaximumLikelihoodEs@ma@on

Page 20: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

[email protected]@veModel

•  P(Y|X)=p(X,Y)/P(X)

•  Genera@vemodel–  LearnP(X,Y)fromtrainingsample–  P(X,Y)=P(Y)P(X|Y)–  Specifieshowtogeneratetheobservedfeaturesxfory

•  Discrimina@vemodel–  LearnP(Y|X)fromtrainingsample– Directlymodelsthemappingfromfeaturesxtoy

Page 21: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Logis@cRegression

Page 22: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Sigmoidfunc@on

•  Defini@on

Page 23: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Logis@cRegression

Page 24: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Logis@cRegression

Page 25: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

MaximizingLogLikelihood

Page 26: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 27: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 28: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 29: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GradientDescent•  Example

Page 30: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

ChangingStepSize

Page 31: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

AddingPrior

Page 32: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 33: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Today’sOutline

•  Perceptron(andkernels)

•  SupportVectorMachines

Page 34: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Perceptron

[SomeoftheslidesareborrowedfromAlexSmola’stutorial]

Page 35: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

BiologyandLearning

•  Idea1:Goodbehaviorshouldberewarded,badbehaviorpunished(ornotawarded).– Raisingadog.

•  Idea2:Correlatedeventsshouldbecombined.– Babieslearnlanguage.

Page 36: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

BiologyandLearning

•  Idea1:Goodbehaviorshouldberewarded,badbehaviorpunished(ornotawarded).– Raisingadog.

•  Idea2:Correlatedeventsshouldbecombined.– Babieslearnlanguage.

•  TrainingMechanisms– Behavioralmodifica@onofindividuals(learning)

•  Feedingthedog,thenthedoglearnstostandandsit.– Hard-codedbehaviorinthegenes(ins@nct)

•  Thewronglycodedanimaldies.

Page 37: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Neurons

Page 38: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Perceptron

Page 39: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Perceptron

•  Weightedcombina@on– Theoutputoftheneuronisalinearcombina@onoftheinputs

•  DecisionFunc@on– Attheendtheresultsarecombinedinto

Page 40: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Perceptron

•  Anabstractmodelistoassumethat

– Wherewistheweight,xisthefeaturevectors

–  bisthebias,•  BiologicalInterpreta@on–  Theweightswicorrespondtothesynap@cweights,themul@plica@oncorrespondstotheprocessingofinputsviathesynapses,andthesumma@onisthecombina@onofsignalsinthecellbody(soma).

Page 41: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

LearningGoal:LinearSepara@on

Page 42: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

PerceptronAlgorithm

Page 43: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

PerceptronAlgorithm•  Nothinghappensifweclassify(xi,yi)correctly•  Ifweseeincorrectlyclassifiedobserva@onweupdatew

andb•  Posi@vereinforcementofobserva@ons

Page 44: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

PerceptronAlgorithm•  Aboutthesolu@on– Weightvectorislinearcombina@onofobserva@onsxi:

Page 45: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

PerceptronAlgorithm•  Aboutthesolu@on–  Classifica@oncanbewri_enintermsofdotproducts:

Page 46: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 47: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 48: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Pseudocode

Page 49: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

TheXORProblem

Page 50: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

TheXORProblem

•  Perceptronscannotlearnsuchlinearlyinseparablefunc@ons!

Page 51: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Problem

•  Linearfunc@onsareo`entoosimpletoprovidegoodes@mators.

Page 52: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Problem

•  Linearfunc@onsareo`entoosimpletoprovidegoodes@mators.

•  Idea:– Maptoahigherdimensionalfeaturespacevia

– Replaceevery by intheperceptronalgorithm.

Page 53: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 54: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 55: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

PerceptrononFeatures

Page 56: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

ProblemswithConstruc@ngFeatures

Page 57: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

ProblemswithConstruc@ngFeatures

•  Needtobeanexpertinthedomain(e.g.Chinesecharacters).

•  Canbeexpensivetocompute.

Page 58: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

PolynomialFeatures•  Dimension=1•  Dimension=2

•  Dimension=d(skipproof)

Page 59: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Kernels

•  Defini@on•  Akernelfunc@on isasymmetricfunc@oninitsargumentsforwhichthefollowingpropertyholds

Page 60: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Somechoicesofkernelfunc@ons

RBFkernel:Radialbasisfunc@onkernel

Page 61: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

LinearKernel

Page 62: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

LaplacianKernel

Page 63: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianKernel

Page 64: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

KernelPerceptron

Page 65: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

LinearSeparators

•  Whichoftheselinearseparatorsisop@mal?

[SomeoftheslidesareborrowedfromDavidSontag’slecture]

Page 66: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 67: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Outline

•  Perceptron(andkernels)

•  SupportVectorMachines

Page 68: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

SupportVectorMachine(SVM)

•  SVMs(Vapnik,1990’s)choosethelinearseparatorwiththelargestmargin.

Hyperplane

Page 69: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

SupportVectorMachine(SVM)

•  Reasons:

–  Intui@on–  Theore@calguarantee(skiphere)–  Inprac@caltasks:SVMbecamefamouswhen,usingimagesasinput,it

gaveaccuracycomparabletoneural-networkwithhand-designedfeaturesinahandwri@ngrecogni@ontask.

Page 70: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

SupportVectorMachine(SVM)

•  Howtofindthehyperplane?

Hyperplane

Page 71: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Planes

•  Aplanecanbespecifiedasthesetofpointsgivenby

Page 72: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Planes

•  Aplanecanbespecifiedasthesetofpointsgivenby

NormalVector:decidethedirec@onoftheplane

Page 73: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Normaltoaplane

Lengthofthevector

Page 74: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Scaleinvariance

Page 75: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model
Page 76: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Whatisthedistance ?γ

Finalresult:canmaximizemarginbyminimizing

Page 77: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Supportvectormachines

Page 78: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Whatifthedataisnotlinearlyseparable?

Page 79: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Whatifthedataisnotlinearlyseparable?

•  Morefeatures

Page 80: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Whatifthedataisnotlinearlyseparable?

Oldobjec@ve

Newobjec@ve

Page 81: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Whatifthedataisnotlinearlyseparable?

Oldobjec@ve

Newobjec@ve

Jointlyminimizew.wandnumberoftrainingmistakes!

Page 82: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Whatifthedataisnotlinearlyseparable?

Page 83: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Allowingforslack:“So`marginSVM”

Page 84: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Allowingforslack:“So`marginSVM”

Page 85: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

PopularToolsforSVMs

•  LIBSVM(c++)– h_ps://www.csie.ntu.edu.tw/~cjlin/libsvm/

•  SVMlight(c)– h_p://svmlight.joachims.org/

•  Scikit-learn(python)– h_p://scikit-learn.org/

Page 86: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

PopularToolsforSVMs

•  Torch(LuaJIT)– h_p://torch.ch/

•  Spider(Matlab)

•  Weka(Java)

Page 87: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Howdoweop@mizetheobjec@ve?

•  Quadra@cprogramming

Page 88: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Kernels

•  Defini@on•  Akernelfunc@on isasymmetricfunc@oninitsargumentsforwhichthefollowingpropertyholds

Page 89: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Howdoweop@mizetheobjec@ve?

•  Quadra@cprogramming

Noplacetoapplythekerneltrick

Page 90: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Constrainedop@miza@on

Page 91: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Constrainedop@miza@on

Page 92: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Constrainedop@miza@on

Page 93: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Lagrangemul@pliers–Dualvariables

•  LagrangeMul@pliers

Page 94: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Howdowesolvewithconstraints?

•  LagrangeMul@pliers

Page 95: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Lagrangemul@pliers–Dualvariables

Page 96: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

BacktoSVM(hardmargin)

Page 97: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

DualSVMderiva@on

Page 98: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

DualSVMderiva@on

Slater’scondi@onfromconvexop@miza@onguaranteesthatthesetwoop@miza@onproblemsareequivalent!(skipproof)

Page 99: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

DualSVMderiva@on

Page 100: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

DualSVMderiva@on

Page 101: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Togetwandb

Page 102: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Classifica@onruleusingdualsolu@onUsingdualsolu@ondotproduct

Page 103: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Dualforthenon-separablecase

Page 104: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Dualforthenon-separablecase

Page 105: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Howtointerpretdualform

Page 106: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Backtotheques@on:Whatifthedataisnotlinearlyseparable?

Page 107: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Forexample:Higherorderpolynomials

Page 108: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Dualformula@ononlydependsondot-productsofthefeatures!

Page 109: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Dualformula@ononlydependsondot-productsofthefeatures!

Page 110: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Kernels

•  Defini@on•  Akernelfunc@on isasymmetricfunc@oninitsargumentsforwhichthefollowingpropertyholds

Page 111: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

KernelTrick

Page 112: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

So`marginSVMwithkernel

Page 113: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

CommonkernelsforSVM

AkaGaussianRadialbasisfunc@on(RBF)kernel

Page 114: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Overficng

•  Hugefeaturespacewithkernels:shouldweworryaboutoverficng?– SVMobjec@veseeksasolu@onwithlargemargin– Goodtheore@calguarantee– Buteverythingoverfitssome@mes

Page 115: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Overficng

•  Hugefeaturespacewithkernels:shouldweworryaboutoverficng?– SVMobjec@veseeksasolu@onwithlargemargin– Goodtheore@calguarantee– Buteverythingoverfitssome@mes

•  Cancontrolby:– SecngC– Choosingabe_erkernel– Varyingparametersofthekernels

Page 116: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Dualforthenon-separablecase

Page 117: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

LinearSVMC=50

Page 118: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

LinearSVMC=50

Page 119: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

LinearSVMC=50

Page 120: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

LinearSVMC=50

Page 121: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Insights

•  ChangingC– ForcleandataCdoesn’tma_ermuch.– Fornoisydata,largeCleadstonarrowmargin(SVMtriestodoagoodjobatsepara@ng,eventhoughitisn’tpossible)

Page 122: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Insights

•  ChangingC– ForcleandataCdoesn’tma_ermuch.– Fornoisydata,largeCleadstonarrowmargin(SVMtriestodoagoodjobatsepara@ng,eventhoughitisn’tpossible)

•  Noisydata– Cleandatahasfewsupportvectors– Noisydataleadstodatainthemargins– Moresupportvectorsfornoisydata

Page 123: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFKernelwithC=0.1

Page 124: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFKernelwithC=0.2

Page 125: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFKernelwithC=0.4

Page 126: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFKernelwithC=0.8

Page 127: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFKernelwithC=1.6

Page 128: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFKernelwithC=3.2

Page 129: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFKernelwithC=6.4

Page 130: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFKernelwithC=12.8

Page 131: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Insights

•  ChangingC–  ForcleandataCdoesn’tma_ermuch.–  Fornoisydata,largeCleadstomorecomplicatedmargin(SVMtriestodoagoodjobatsepara@ng,eventhoughitisn’tpossible)

– OverfiMngforlargeC•  Noisydata–  Cleandatahasfewsupportvectors– Noisydataleadstodatainthemargins– Moresupportvectorsfornoisydata

Page 132: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

CommonkernelsforSVM

AkaGaussianRadialbasisfunc@on(RBF)kernel

Page 133: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFwithdifferent

Page 134: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFwithdifferent

Page 135: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFwithdifferent

Page 136: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

GaussianRBFwithdifferent

Page 137: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Insights

•  Changing–  Forcleandata, doesn’tma_ermuch.–  Fornoisydata,small leadstomorecomplicatedmargin(SVMtriestodoagoodjobatsepara@ng,eventhoughitisn’tpossible)

–  Lotsofoverficngforsmall•  Noisydata–  Cleandatahasfewsupportvectors– Noisydataleadstodatainthemargins– Moresupportvectorsfornoisydata

Page 138: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Homework(partofassignment2)

•  Studythe“Sequen@alMinimalOp@miza@on”algorithmandimplementanSVMclassifierbyyourself

•  References– h_p://cs229.stanford.edu/materials/smo.pdf– FastTrainingofSupportVectorMachinesusingSequen@alMinimalOp@miza@on

– h_p://research.microso`.com/pubs/68391/smo-book.pdf

Page 139: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Whatwelearnedtoday

•  Perceptron(andkernels)

•  SupportVectorMachines

Page 140: CS 6140: Machine Learning - College of Computer … · What we learned last @me • Evaluaon metrics • Decision Tree • Generave Models • Generave Model and Discriminave Model

Homework

•  ReadMurphyCH14.1-14.2,14.4-14.5.•  Assignment1isout.Dueintwoweeks.