JDINearRepeatToolKit–Manual
ThismanualdescribeshowtousetheJDINearRepeatToolKit,whichperformsspace-time
clusteringanalysisongeo-referencedcrimedataandprovidesinteractivemappingofresults.
Thefollowingsectionsdescribehowthesoftwarecanberun,andhowitcanbeappliedto
crimedataprovidedbytheuser.
Whatthesoftwaredoes
ThesoftwareperformstwoversionsoftheKnoxtestforspace-timeclustering:aunivariate
andbivariateform.Fulldetailsofthesestatisticaltests,asimplementedhere,aregiveninthe
followingthreepapers:
•
JohnsonSD,BernascoW,BowersKJ,ElffersH,RatcliffeJ,RengertG,andTownsleyMT
(2007). Space-Time Patterns of Risk: A Cross National Assessment of Residential
Burglary.JournalofQuantitativeCriminology,23(3),201-219.
•
JohnsonSD,SummersLandPeaseK(2009).OffenderasForager?ADirectTestofthe
BoostAccountofVictimization.JournalofQuantitativeCriminology,25(2),181-200.
•
Braithwaite A and Johnson SD (2012). Space–Time Modeling of Insurgency and
CounterinsurgencyinIraq.JournalofQuantitativeCriminology,28(1),31-48.
Thesoftwaretakesasitsinputcrimeincidentdataprovidedbytheuser.Thedatamustbe
providedinCSVformat(thiscanbegeneratedbyspreadsheetpackagessuchasMSExcel)
andeachincidentmustberepresentedbyarow.Theinputdatamustcontainthefollowing
fields:
•
Auniqueidentifierforeachincident,suchasacrimereferencenumber.
•
Thetypeofoffence(e.g.‘Residentialburglary’).
•
Thedateoftheoffence(e.g.‘Recordingdate’).
•
The location of the offence. This must be provided in OS British National Grid
(EPSG:27700)format,withseparatefieldsforEastingandNorthing.
Citation
Ifyouusethissoftwareforresearch,pleaseciteitusingthefollowingform:
•
Davies TP and Johnson SD (2016). JDI Near Repeat ToolKit. Available at:
http://www.ucl.ac.uk/jdibrief/analysis/space-time-pattern-analysis.
Requirements
The ToolKit is a Windows-only application, and is designed for versions 7 and above. It is
recommendedthatisshouldberunonPCswithatleast2GBRAM,andprocessorspeedof
1.6GHz+.Inaddition,aninternetconnectionisrequiredformappingofresults.
Installation
The ToolKit is a stand-alone programme and requires no installation. Simply unzip the
downloadedarchivetoanylocation,anddouble-clickthefile‘JDINearRepeatToolKit’.This
willlaunchthetool.
PerformingAnalysis
Usage of the ToolKit is divided into three stages: 1) Data loading, 2) Data and parameter
selection,and3)Resultexamination.Eachofthesewillbedescribedinturn.
Dataloading
WhentheToolKitislaunched,thedataselectioninterfaceappears.Sincenodatahasyetbeen
loaded,mostitemsaregreyedout.Inordertoimportdata,eitherselectFile->Loaddataor
usethekeyboardshortcutCtrl+L.
ThiswillopentheOpenfiledialogbox,whichiswherethefilecontainingcrimedatawillbe
identified.ClickBrowse…andlocatethedatafileonyourcomputer.ThismustbeaCSVfile,
witheachrowrepresentinganindividualincident.
Afterselectingthedatafile,itisnecessarytoidentifythecolumnswhichcontaintherequired
information for the analysis. Select these from the drop-down menus in each case. It is
important that the Recording date format field gives the exact format in which date
informationisrecordedinthefile–notethatthismaybedifferenttotheformitappearsin
MSExcel,whichappliesautomaticformatting.
ClickingOKwillreturntothemainscreen,wheretheDatapropertiespanelwillhavebeen
updatedwithsomesimpledescriptivestatisticsforthedata.Ifnoincidentshavesuccessfully
loaded,orthenumberislowerthanexpected,thissuggeststhatanerrorhasoccurredinthe
loadingstage.EnsurethattheCSVsourcefileisformattedcorrectlyandthatallfieldshave
beencorrectlyidentified.
Dataandparameterselection
Nowthatdatahasbeenloaded,theanalysisitselfcannowbesetup.Thefirststageofthisis
toselecttheincidentsthatwillbeincludedintheanalysis,whichcanbedonebychanging
thesettingsintheDataselectionpanel.Onlyincidentswhichliewithinthespecifiedspatial
limits,andwithinthetemporalbounds,willbeconsidered.
ThePrimaryoffenceandSecondaryoffenceselectionsrefertotheincidenttypesthatwillbe
consideredintheanalysis.Ifthesameoffenceischosenforbothfields,asimpleunivariate
Knox test will be performed; if the offences are different, the bivariate Knox test will be
performedinstead.
TheAnalysisparameterspanelcontainsthesettingswhichwillbeusedinperformingthe
Knoxtest.Theparametersareasfollows:
•
The Temporal bandwidth and Spatial bandwidth settings determine the proximity
thresholdswhichwillbeusedineachdimension.
•
Thenumberofbandscanalsobespecifiedinbothcases–if5bandsof200metres
areused,forexample,thiswillconsiderclosepairsupto1,000metresapart.
•
IftheSamedayorSamelocationboxesareticked,thiswilladdaseparatebandfor
exactmatchesineitherdimension.
•
Numberofiterationsdeterminesthenumberofpermutationswhichwillbeusedin
the test – a higher number will allow significance to be established with greater
resolution,butwilltakelongertorun.
•
TheRespectorderingtickboxdetermineswhethertheorderingofincidentsistaken
intoaccount–ifticked,pairswillonlybeconsideredifthesecondaryoffenceoccurs
aftertheprimaryoffence.
Oncethedesiredsettingshavebeenentered,clickAnalysetoperformthetest.
Resultexamination
Aftersomeprocessingtime,theAnalysisresultsdialogwilllaunch.TheResultspanelonthe
leftshowstheKnoxtable,withonerowforeachtemporalbandandonecolumnforeach
spatialband.ThenumbersinthecellsareKnoxratios,whichrepresenthowmanymoretimes
pairsoccuratthecorrespondingthresholdsthanthemedianvaluethatwouldbeexpectedif
noclusteringwaspresent.Thecellsarecolouredaccordingtothesevalues,withthescale
givenabovethetable.Thevaluesfromthistablecanbecopiedandpastedtoanexternal
programme,suchasMSExcel.
Thepanelontherightshowsamapoftheanalysisregion,withincidentsplottedandnearrepeatpairsidentified.Thisallowstheusertoseewhichincidentsarecontributingtoany
clusteringpatternsthatarepresent(NOTE:theincidentsshownherehavebeengenerated
randomlyanddonotcorrespondtorealevents).
TheMapsettingspanelontheleftcanbeusedtoconfiguretheappearanceofthedisplay.
TheClosepairdistanceandClosepairtimeoptionsdeterminewhicharrowsareshown–
they will be placed between all pairs of incidents lying within these threshold values (so
choosinglowervalueswillshowshorter-rangenearrepeatsonly).Theotheroptionsallow
aestheticchangestobemadetothedisplayofthemapandthesizesoftheicons.
Themapshownontherightisinteractive,andcanbenavigatedandinterrogatedusingthe
buttonsatthebottomofthemap.
ClickingthePan/Zoom
iconallowsnavigationwithinthemap.Tozoom,placethemouse
overthemapimageandusethemousewheelorotherscrollingdevice.Forlargerareas,there
maybesomedelaywhenzoomingin,butthemapwilleventuallyload.
TheIdentify
toolcanbeusedtoexaminedetailsofparticularincidents.Whenactivated,
clickingincidentsonthemapwilllaunchadialogshowingthecrimenumber,dateandoffence
typeofthecrimeinquestion.
TheSave
iconallowsthedisplayedimagetobesavedexternally.Theimagewillbesaved
exactly as it currently appears in the map pane (i.e. at the current pan/zoom) and can be
exportedinanumberofformats,includingPNG.