南航暑期国际课程大数据可视化第8讲3

DensePixelDisplaysIdea–mappingeachdimensionvaluetoacoloredpixel(onepixelperdatavalue)andgroupthepixelsbelongingtoeachdimensionintoadjacentareas.E.g.,(5,3,4,7)ismappedto4coloredpixelslocatedonenexttoeachother.Thistechniquesallowthevisualizationofthelargestamountofdatapossibleoncurrentdisplays(uptoabout1.000.000=103x103datavalues).Densepixeltechniquesusedifferentpixelarrangementsfordifferentpurposes.Theresultingvisualizationprovidesdetailedinformationonlocalcorrelations,dependencies,andhotspots.DensePixelDisplays

(1)Recursivepattern(2)CirclesegmentsTherecursivepatterntechnique--arecursiveback-and-fortharrangementofthepixelsE.g.,representingdatasetswithanaturalorderaccordingtooneattribute(e.g.timeseriesdata).Toformsemanticallymeaningfulsubstructurestheusermayspecifyparametersforeachrecursionlevel.ArrangementsThebaseelementoneachrecursionlevelisapatternwithinrectanglesofheighthiandwidthwiasspecifiedbytheuser.Pixelsinarectangleh1xw1arefirstarrangedfromlefttoright,thenbelowbackwardsfromrighttoleft,thenagainforwardfromlefttoright,andsoon.Thesamearrangementisdoneonallrecursionlevelswiththeonlydifference

thebasicelementswhicharearrangedonleveliarethepatternresultingfromthelevel(i−1)arrangements.Recursion

DensePixelDisplays:

attributemapping(setsof1-Dmappings)5Examplesofrecursivepatternlayouts.a1a2a3a4objectsattributesx1x2x3x4x5…xn13428…526710…096114…645272…9

DensePixelDisplays:objectsmapping(n-Ddatamappingsside-by-side)6Examplesofrecursivepatternlayouts.x1x2x3x4x5…xn13428…526710…096114…645272…9a1a2a3a4Objects,e.g.,stocksattributesWorkswellfortimeserieswheneachattributexirepresentsthesameattributebutatdifferenttime,e.g.,stockprice

DensePixelDisplaysExamplesofscreen-fillinglayouts.Data:twentyyears(January1974-April1995)ofdailypricesofthe100stockscontainedintheFrankfurtStockIndex(FAZ).(~250tradingdays/year)x20yearsx100stocks=500,000numbers(pricesrepresentedaspixels)~(700x700pixels)ExampleofrecursivepatternvisualizationoffinancialdataEachcolumncontains25stocksTheidea--representingthedatainacircledividedintosegments,oneforeachattributeorobject.Withinthesegmentseachattributevalueisvisualizedbyasinglecoloredpixel.Circlesegmentstechnique

visualizationofdailystockpricesof50stocksover20years.EachsegmentisastockThearrangementofthepixelsstartsatthecenterofthecircleandcontinuestotheoutside.Pixelsareplottedonalineorthogonaltothesegmentcuttinguplineinabackandforthmanner.Therationalofthisapproachisthatclosetothecenterallattributesareclosetoeachotherenhancingthevisualcomparisonoftheirvalues.Circlesegmentstechnique

Infactthedensedisplayisasetofone-dimensionalprojecti