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TheKevinBaconGame

Haveyoueverrunintoafriendsomewhereyoudidn’texpectto?Haveyouevermetsomeone

newandfoundoutyouhadfriendsorfamilyincommon?Whenthishappens,weoftensay

Well,there’sanetworkforthat!

Smallworldnetworksareatypeofnetworkusedto

modelasocialgrouporsocialconnections.

Q:Whyaretheycalledsmallworldnetworks?A:Inasmallworldnetwork,thepathfromanygivennodetoanyothernodewillberelativelyshort.Inotherwords,themeanpathlengthisshort.

(ericwrobbel.com)

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Thepopularideaofthesixdegreesofseparation,firstexploredbypsychologistStanley

Milgraminthe1950s,describeshumansocietyasasmallworldnetworkwherethemeanpath

lengthissix.(Ifyou’renotfamiliarwiththeideaofthesixdegreesofseparation,clickhereto

learnmore.)

TheKevinBacongamecameoutoftheideaofthesixdegreesofseparation,andissometimes

calledtheSixDegreesofKevinBacon.Givenanyactressoractor,thegoalistolinkthatperson

toKevinBaconintheleastamountofstepspossible.Thenumberofstepsiscalledsomeone’s

Baconnumber.ItisalmostimpossibletofindanyonewithaBaconnumberhigherthansix!

GooglehasahiddenBaconnumberfeature!Searchthenameplus“BaconNumber.”

Lookatthegraphtotheleft.Isthereapathlongerthan6steps?

Pickanystartingnodeinthegraph/networkontheleft.

Nowpickanendingnode.

Countthenumberofedgesbetweenthem.Thisisthelengthofyourpath.

(Wikipedia)

EXAMPLE1:WhatisWillSmith’sBaconnumber?

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Let’sgetstarted!

ActivitiesOverviewYouwillcreateasmallworldnetworkfromtheKevinBacongame.You’llreviewandusetheseconcepts:

1. Breeds2. Links3. Labels4. Degree5. Thenetworkextension/networkformatting

You’lllearnthesenewconcepts:

1. Influenceofanode(Eigenvectorcentrality)2. foreach(loopsandnestedloops)

EXAMPLE2:MakeagraphofExample1.

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InfluenceofaNode(Eigenvectorcentrality)Eigenvectorcentralityisacomplicatednameforasimpleconcept:ifyourfriendshavealotof

influence,thenyouprobablydotoo.We’lljustcallitinfluencefromhereon.Influenceisa

decimalvaluebetween0and1.Avalueof0indicatesthatanodehasminimuminfluenceona

graph,andavalueof1indicatesthatanodehasthemaximuminfluenceonagraph.

InNetLogo,wecancalculatetheinfluenceofanodebyusingthenetworksextension.Besure

toincludeitatthetopofeachfileasyoudidinthepreviousactivities.

Wecanmakeamonitortoobserveanode’sinfluencelikethis:

Whydowecareaboutinfluence?Ifwecanidentifyinfluentialnodesinagraph,wecanlearnmoreaboutthesetypesofsituations:

• Whostartsfashiontrendsamongfriends?

• Whichcountry’seconomyhasthemosteffectonothercountriesintheregion?

• Ifthere’sanoutbreakofavirus,who’sthemostatriskofspreadingittootherpeople?

(Youwillmodelavirusoutbreakinthenextlesson!)

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Noticethenw: beforeeigenvector-centrality.Thenw: tellsNetLogotolookinthe

networksextensiontofindtheeigenvector-centralitycommand.

Rememberthatwecanusebreedstonameour turtles

whateverwewant(herewenamedthempeople). Also,

wecanuselabelstotellourpeopleapart.

foreachInthelastlesson,wehadtomakeeachedgebyhand.Byusingforeach,wecansimplymakealistofnodeswewanttomakeoraddpropertiesto,andthenspecifyagenericbehaviorforeachofthem.(Ifyou’renotfamiliarwithlistsinNetLogo,gohere.)Let’sstartwithasimpleexample.Let’smakealistofnumbersanduseforeachtoshowthem:Howaboutsomethingalittlemoreinteresting?Let’susethesamelist,butcreateturtlesinstead:

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TROUBLESHOOTINGforeachblocks

• youmayhavetoaddparentheses,likethis:

(foreach num move [create-turtles ?1] [ask turtles [forward ?2]])

(Here,moveisanotherlist.)

Activity1:KevinBaconCreateanewNetLogofile.Nameityourlastname_yourfirstname_BaconGame.nlogo.

WHAT’STHATQUESTIONMARKABOUT?• NetLogoprocessesalistinorderwhenaforeachloopusesit.The?is

theelementinthelistthatNetLogoiscurrentlyusing.

• Intheexampleabove,NetLogowillcreate1turtle.Then,itwillgotothe

nextelementintheloopandcreate2turtles,then3,then4.

• Ifyou’reworkingwithmultiplelists,youcanuse?1,?2,etc.

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RefertotheboxbelowforanexampleofpeoplewithBaconnumberoneandBaconnumbertwo,orfindyourownusingtheGoogletoolmentionedearlier.

1. Createabreedofpeople.2. Createabacon-game procedureandaddabuttonforitontheinterfacetab.Your

bacon-game procedureshouldclear-allandsetthedefaultshapeofyourpeopleto“person”.Then,yourbacon-game proceduremustcallthefollowingprocedures:• setup-kevin-bacon• setup-bacon-number-one• setup-bacon-number-two• setup-intermediate-links• setup-size-degree

3. Createtheproceduresfrom2).Theydon’tneedbuttons.Usethetablebelow.setup-kevin-bacon

Createaperson.Setitslabelto“KevinBacon.”

BACONNUMBERof1MichaelFassbender--X-MenFirstClassw/KevinBaconIdrisElba--X-MenFirstClassw/KevinBaconJenniferLawrence--X-MenFirstClassw/KevinBaconAndyGarcia--TheAirIBreathew/KevinBaconJohnLithgow--Footloosew/KevinBaconBACONNUMBERof2PenelopeCruz--TheCounselorw/MichaelFassbenderBeyoncé--Dreamgirlsw/JohnLithgow

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setup-bacon-number-one

Makealist.Thelistshouldcontainthelabels(names)ofeveryonewithaBaconnumberofone.foreachofthenamesinyourlist,createaperson,settheirlabeltothelistvalue,andlinkthemtoKevinBacon.

setup-bacon-number-two

Make2lists.Thefirstlistshouldcontainthelabels(names)ofeveryonewithaBaconnumberoftwo.Thesecondlistcontainsthecorrespondingpersonlinkedwiththepersoninthefirstlist.Tobeclear,thefirstpersoninthefirstlistislinkedwiththefirstpersoninthesecondlist.Thesecondpersoninthefirstlistislinkedwiththesecondpersoninthesecondlist…etc.Youalreadycreatedthepeopleinthesecondlistinsetup-bacon-number-one.foreachofthelabelsinlistone,createapersonandmakealinkwiththecorrespondingpersoninlisttwo.

setup-intermediate-links

Allofthesepeoplestarredinthesamemovie.Maketwoidenticallistsoftheirlabels(names).foreachofthepeopleinlistone,gothroughthesecondidenticallist(withanestedforeach)andmakelinkswitheveryone(exceptthemselves).

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setup-size-degree

Setthepeoples’sizetotheirdegree.(Wecangetthedegreeofapersonbycountinghowmanylink-neighborsthereare.)

4. Usealayouttoorganizethenodes.Putthiscodeattheendofyourbacon-gameprocedure.

5. Createthefollowingmonitors.(Lookatpage4ofthisdocumentforadditionalhelpwiththeInfluencemonitors):

DegreeofKevinBacon[countlink-neighbors]ofpeoplewith[label="KevinBacon"]AverageDegreeofNetworkmean[countlink-neighbors]ofpeopleDegreeofJ.LawrenceInfluenceofKevinBacon[nw:eigenvector-centrality]ofpeoplewith[label="KevinBacon"]AverageInfluencemean[nw:eigenvector-centrality]ofpeopleInfluenceofJ.LawrenceInfluenceofM.FassbenderInfluenceofBeyonce

HINTS:

1. Don’tforgettoincludethenwextension.2. Turnoffworldwrapping,oryouredgeswilllookcrazy.

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TurninginYourProjectPre-submissionchecklist

¨ Isyourname,date,andprojecttitleatthetopofyourfileincomments?¨ Isyourcodeorganizedandformattedtocoursestandards?¨ Doesitworkwithouterrors?¨ Isyourfilenamedcorrectly?

IfyouansweredYEStoallofthesequestions,congrats!Youarereadytoturninyourproject.Youwillbegiveninstructionsforhowtoturn-ininclass.

Rubric

Networks2:TheKevinBaconGame(10points)

Points Tasktobecompleted

2Clarityandprofessionalism:Yourfileisnamedandcommentedappropriately.[1point]Thecodeisformattedandisreadable.[1point]

8Activity1:TheKevinBaconNetworkActivityiscompleteandworksasexpected.[8points]