identifying remarkable researchers using citation network analysis ephrance abu ujum faculty of ...

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IDENTIFYING REMARKABLE RESEARCHERS USING CITATION
NETWORK ANALYSIS
EPHRANCE ABU UJUM
FACULTY OF SCIENCE
UNIVERSITY OF MALAYA
KUALA LUMPUR
2014
IDENTIFYING REMARKABLE RESEARCHERS USING
CITATION NETWORK ANALYSIS
EPHRANCE ABU UJUM
DISSERTATION SUBMITTED IN FULFILMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
INSTITUTE OF MATHEMATICAL SCIENCES
FACULTY OF SCIENCE
UNIVERSITY OF MALAYA
KUALA LUMPUR
2014
UNIVERSITI MALAYA
ORIGINALLITERARYWORKDECLARATION
NameofCandidate: EPHRANCEABUUJUM
I.C./PassportNo.: 780923-12-5195
Registration/MatricNo.: SGP070002
NameofDegree: MASTEROFSCIENCE
TitleofProjectPaper/ResearchReport/Dissertation/Thesis(“thisWork”):
“IDENTIFYINGREMARKABLERESEARCHERSUSINGCITATIONNETWORKANALYSIS”
FieldofStudy: MATHEMATICALMODELING
Idosolemnlyandsincerelydeclarethat:
(1) Iamthesoleauthor/writerofthisWork;
(2) Thisworkisoriginal;
(3) Anyuseofanyworkinwhichcopyrightexistswasdonebywayoffairdealingandforpermitted
purposesandanyexcerptorextractfrom,orreferencetoorreproductionofanycopyrightwork
hasbeendisclosedexpresslyandsufficientlyandthetitleoftheWorkanditsauthorshiphave
beenacknowledgedinthisWork;
(4) Idonot haveanyactual knowledgenordo Iought reasonably toknow thatthemaking ofthis
workconstitutesaninfringementofanycopyrightwork;
(5) I hereby assign all and every rights in the copyright to this Work to the University of Malaya
(“UM”),whohenceforthshallbeownerofthecopyrightinthisWorkandthatanyreproduction
oruseinanyformorbyanymeanswhatsoeverisprohibitedwithoutthewrittenconsentofUM
havingbeenfirsthadandobtained;
(6) IamfullyawarethatifinthecourseofmakingthisWorkIhaveinfringedanycopyrightwhether
intentionallyorotherwise,Imaybesubjecttolegalactionoranyotheractionasmaybedeter-
minedbyUM.
(CandidateSignature) Date:
Subscribedandsolemnlydeclaredbefore,
Witness’sSignature Date:
Name: PROFESSOR DR KURUNATHAN A/L RATNAVELU
Designation: PROFESSOR
ii
ABSTRACT
Experts or authorities within a research field exhibit specific traits in how they pub-
lish as well as in how they are cited by others. An analysis of such citation dependen-
cies requires a network approach whereby a researcher’s impact depends not only on the
number of citations he/she has accumulated (over a given period of time) but also on
the prominence of researchers who depend on their work. This thesis shall explore how
to distinguish researchers based on temporal patterns of their publication and citation
records.
Asintuitionmaysuggest,theinfluenceofaresearcherisproportionaltothenumber
ofcitationshe/shehasacquiredaswellastheinfluenceofhis/hercitingauthors. Authority
canalsobeconferredtoaresearcherbyvirtueofhis/her(co)authoredworksthatcontinue
toaccruecitationslongaftertheyearofpublication.
In this thesis, experts or authorities are identified using the “temporal citation net-
work analysis” approach of Yang, Yin, and Davison (2011). This method assigns a high
influencescoretoresearcherswhoarestillactivelyandpersistentlypublishing,havelong
publicationtrackrecord,andareheavilycited(especiallybyinfluentialpeers).
Asacasestudy,themethodproposedbyYangandco-workersshallbeusedtoiden-
tify authorities within the ISI Web of Knowledge category of “BUSINESS, FINANCE”
spanning the period 1980-2011 inclusive. The thesis shall also explore a modification of
thismethodtopredictrisingstarswithinthesamedataset.
iii
ABSTRAK
Pakardalamsesebuahbidangpenyelidikanmenunjukkanciri-cirikhususdalamcarame-
reka menerbitkan artikel dan juga dalam cara mereka dirujuk penyelidik lain. Anal-
isa kebergantungan pemetikan perlu didekati dengan menggunakan konsep rangkaian di
manaimpakseseorangpenyelidiktidakhanyabergantungkepadajumlahpemetikanyang
diperolehi (dalam suatu jangka masa tertentu), tetapi juga pada kewibawaan penyelidik-
penyelidiklainyangbergantungkepadakaryadanciptaannya.
Disertasiinimeneliticaramembezakanpenyelidikdenganmengeksploitasikanpola
bataswaktudalamrekodpenerbitandanpemetikanmereka. Sepertiyangdicadangkanin-
tuisi,pengaruhseseorangpenyelidikberkadarterusdenganjumlahpemetikanyangdiper-
olehi serta pengaruh penyelidik yang memetik artikelnya. Kewibawaan turut diberikan
kepadaseseorangpenyelidikmenerusikaryakongsiyangmenerimapemetikanbeterusan
walaubertahunlamasejaktahunpenerbitan.
Disertasiiniakanmengenalpastipakardenganmenggunakankaedah“temporalcita-
tionnetworkanalysis”yangdisarankanolehYangetal.(2011). Kaedahinimemberiskor
pengaruh yang tinggi kepada penyelidik yang masih aktif dan menerbitkan artikel secara
beterusan, mempunyai rekod penerbitan yang ekstensif, dan juga dipetik secara intensif
(terutamasekalidaripadakumpulanyangberpengaruh).
Sebagai kes kajian, kaedah yang disarankan oleh Yang et al. akan digunakan un-
tukmengenalpastipakar-pakardalamkategorisubjek“BUSINESS,FINANCE”daripada
pangkalan data ISI Web of Knowledge dalam jangka waktu merentangi tahun 1980 se-
hingga (dan termasuk) tahun 2011. Disertasi in juga meneliti modifikasi kaedah Yang et
al.untukmeramalpakaryangakandatangdenganmenggunakansetdatayangsama.
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ACKNOWLEDGEMENTS
First and foremost, I offer thanks to God for giving me the opportunity to explore ideas.
I express great gratitude to my supervisor Professor Dr. Kurunathan Ratnavelu for his
unwaveringsupportandbeliefinmeovertheyears. Hisguidanceandwisdomhasmade,
and will continue to make an enduring impact on my life. I also wish to express heartfelt
gratitudetomycollaboratorandfriend,Dr.ChoongKwaiFatt,forrelentlesslyencourag-
ingthepursuitofthisworkandotherrelatedproblems.
I hereby thank the hardworking staff of the Institute of Mathematical Sciences, Fac-
ulty of Science, and the Institute of Postgraduate Studies for their invaluable help and
counselling especially during various setbacks I faced during the completion of this the-
sis. I am profoundly indebted to their patience and generosity. Some critical directions
inthisworkwasdevelopedundergrantsRG146/10HNEandRG298/11HNEprovisioned
undertheUMRGscheme,andlaterthroughtheUMHighImpactResearch(HIR)grant.
IwishtothankThomsonReutersforthedatausedinthisthesis,obtainedspecifically
viainstitutionalaccesstotheWebofKnowledge. Ialsowishtoacknowledgetheingenuity
oftheOpenSourcecommunity,specificallyinLinux,R,Perl,Python,Gephi,andLATEX.
To my friends and colleagues: I am grateful to Chin Jia Hou, Melody Tan, and Tan
HuiXuanforthehelptheyhavegivenmefromtimetotime. Agreatdealoftheideasand
questions pursued in this work stemmed from useful discussions I have had with these
wonderful people. All in all, I owe my family for their endless love and understanding,
without which this work would have been impossible to accomplish. It is to them that I
dedicatethiswork.
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TABLEOFCONTENTS
ORIGINALLITERARYWORKDECLARATION ii
ABSTRACT iii
ABSTRAK iv
ACKNOWLEDGEMENTS v
TABLEOFCONTENTS vi
LISTOFFIGURES viii
LISTOFTABLES ix
LISTOFAPPENDICES xi
CHAPTER1: INTRODUCTION 1
1.1 Background 1
1.2 LiteratureReview 5
1.2.1 Quantifyingauthorityandexpertise 5
1.2.2 Identifyingauthoritiesandexpertsonnetworks 13
1.2.3 Citationnetworkofresearchpapers 25
1.2.4 Citationnetworkofauthors 28
CHAPTER2: METHODOLOGY 30
2.1 Definitionsandnotation 30
2.1.1 Basicdefinitions 30
2.1.2 Networkproperties 32
2.2 Data 34
2.2.1 Processingthedata 34
2.2.2 Extractingcitations 50
2.3 Networkanalysis 53
2.3.1 Documentcitationnetwork(DCN) 53
2.3.2 Authorcitationnetwork(ACN) 56
2.3.3 Yang-Yin-Davisonlinkweightingscheme 59
2.3.4 Goodnessofprediction 61
2.4 OutlineofMethodology 62
2.5 Softwareused 65
CHAPTER3: ANALYSIS 67
3.1 Documentcitationnetwork 67
3.2 Journalcitationnetwork 77
3.3 Identifyingexpertsandauthorities 88
3.4 Identifyingrisingstars 98
vi
CHAPTER4: CONCLUSION 104
APPENDICES 109
REFERENCES 143
vii
LISTOFFIGURES
Figure2.1 ISIdatafieldtags 37
Figure2.2 SampleISIdata 38
Figure2.3 ParsingISIdata. 63
Figure2.4 Snapshotofdocumentcitationnetwork(DCN)centredonone
paper,i.e.“fama.ef_1993_j.financ.econ_v33_p3”. Numerical
valuesonlinkscorrespondstoCIR values. Inset: illustrationof
hierarchicalstructureduetotimeorderingofpapersontheDCN. 64
Figure2.5 Snapshotofauthorcitationnetwork(ACN)centredononeauthor,
i.e.“fama.ef”. NumericalvaluesonlinkscorrespondstoCI values. 64
Figure2.6 OutlineofCoarse-Grain(CG)scheme. 65
Figure2.7 OutlineofYYDscheme. 65
Figure3.1 Giantweaklyconnectedcomponentofdocumentcitationnetwork
(DCN).Nodesarecolor-codedviacommunitydetectionmethod
ofBlondel,Guillaume,Lambiotte,andLefebvre(2008)and
plottedusinganopensourcegraphvisualisationandexploration
toolcalledGephi(Bastian,Heymann,&Jacomy,2009). 68
Figure3.2 Documentcitationnetwork(DCN)fornodesinthetop20listby
citationcount(in-degreecentrality). Nodesarecolor-codedbyyear
andsizedbycitationcountontheentireDCN.PlottedwithGephi. 72
Figure3.3 Documentcitationnetwork(DCN)fornodesinthetop20listby
PageRank. Nodesarecolor-codedbyyearandsizedbyPageRank
scoreontheentireDCN.PlottedwithGephi. 72
Figure3.4 Journalcitationnetworkfor“Business,Finance”(1980–2011).
Communitydetectionwascarriedoutusingthehierarchical
optimizationofmodularitymethoddevelopedbyBlondelet
al.(2008). Community(module)membershipisaslisted
inTable3.4. PlottedwithGephi. 78
Figure3.5 Giantweaklyconnectedcomponentofauthorcitationnetwork
(DCN).Nodesarecolor-codedviacommunitydetectionmethod
ofBlondeletal.(2008)andplottedusingGephi. 89
Figure3.6 ScatterplotofcorrelationmatrixinTable3.8. Graphicisproduced
usingthePerformanceAnalyticspackageinR(Carl,Peterson,
Boudt,&Zivot,2009). 90
FigureA.1 Aseminalpaperspansastructuralholeinthecitationnetwork,
i.e.,advancesworkindifferentgroupsofdenselyconnectedpapers
(indicatedbydifferentcolours). 117
FigureA.2 Anintegrativepapercitesasetofpapersthatthemselvesdonot
citeeachother. 119
viii
LISTOFTABLES
Table1.1 Numberofarticlesin30journalsunderthe“BUSINESS,
FINANCE”dataset,thatmaintainforward/reversealphabetical
orderingatleast50%ofthetime. Eachjournalhasatleast50
articlesco-authoredby2ormoreworkersovertheperiod
2005–2010. 8
Table2.1 Sourcedataparameters 34
Table2.2 Coverageofarticlesandcitationswithinthe“Business,Finance”
studydataset. Seetextfordetails. 42
Table2.3 Citationandin-degreestatistics. 51
Table3.1 Propertiesofdocumentcitationnetwork(DCN). 68
Table3.2 Thetop20citedarticles. JAR,JF,JFE,andRFSdenotethejournals
JournalofAccountingResearch,TheJournalofFinance,Journalof
FinancialEconomics,andReviewofFinancialStudies,respectively.
Theasterisk(*)denotesarticleswithPageRank-to-CiteRank
ratiolargerthan10. 73
Table3.3 Thetop20articlesbyGooglePageRankscore. JF,JFE,JME,and
MFdenotethejournalsTheJournalofFinance,Journalof
FinancialEconomics,JournalofMonetaryEconomics,and
MathematicalFinance,respectively. Theasterisk(*)denotes
articleswithCiteRank-to-PageRank ratiolargerthan10. 74
Table3.4 ModulemembershipforjournalsinFigure3.4. 79
Table3.5 Centralityof“Business,Finance”journalsbasedoninter-journal
citationlinksspanningthe5-yearperiod2007–2011. Journalsare
listedbydecreasingstructuralinfluencescore,S. C ,C ,C ,
D C B
denotedegree,closeness,andbetweennesscentrality,respectively.
Theinandoutsuperscriptsdenotein-linkandout-linkversionsof
thecorrespondingcentralityalgorithm. PR0.86,PR0.5,auth,and
hubdenotestheGooglePageRankscorewithd = 0.86,PageRank
withd = 0.5,HITSauthority,andHITShubscore,respectively. 82
Table3.6 Rankof“Business,Finance”journalsbasedoninter-journalcitation
linksspanningthe5-yearperiod2007–2011. Journalsarelistedby
decreasingstructuralinfluencescoreS. 86
Table3.7 Propertiesofauthorcitationnetwork(ACN). 88
Table3.8 Spearmanrankcorrelationcoefficientfornodeattributesongiant
componentoftheauthorcitationnetworkconstructedinthisstudy.
h-indexscoresareestimatedbasedonarticleslimitedtojournalsin
thestudydataset(i.e.ISI-indexedarticlespublishedunder
the“Business,Finance”subjectcategoryspanningtheperiod
1980-2011). Valuesinthelowertrianglecorrespondtocorrelation
p-values. 90
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