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1、Cours de Visualisation dInformationInfoVis LectureHierarchies and Trees 2Frdric VernierEnseignant-Chercheur LIMSI-CNRSMatre de conf Paris XI,Inspired from CS 7450-Information VisualizationJan.10,2002John Stasko,2,Node-link Shortcoming,Difficult to encode more variables of data cases(nodes)ShapeColor
2、 Sizebut all quickly clash with basic node-link structure,3,Space-Filling Representation,Each item occupies an areaChildren are“contained”under parent,One example,4,Treemap,Space-filling representation developed by Shneiderman and JohnsonChildren are drawn inside their parentAlternate horizontal and
3、 vertical slicing at each successive levelUse area to encode other variable of data items,5,Treemap,Example,Directories,6,Treemap,7,Treemap Algorithm,Draw()Change orientation from parent(horiz/vert)Read all files and directories at this level Make rectangle for each,scaled to size(Slicing)Draw recta
4、ngles using appropriate size and color For each directory Make recursive call using its rectangle as focus,8,Nested vs.Non-nested,Nested Tree-Map,Non-nested Tree-Map,9,Applications,Can use Treemap idea for a variety of domainsFile/directory structuresBasketball statisticsSoftware diagramsTennis matc
5、hes,10,Software Visualization App,SeeSys:Software Metrics Visualizing SystemUses treemap-like visualization to present different software metricsDisplays:SizeRecent developmentHigh fix-on-fix ratesHistory and growth,Baker and Eick 95,11,Sample View 1,Subsystems in a software system.Each rectangle re
6、presents thenon-comment source code in a subsystem.Area means size,New codein this release,Size,12,Sample View 2,Bug rates by subsystem and directory,Representsnew codein this release,Bug fixes,Addedfunctionality,Bars representindividualdirectories inthe subsystems,13,Tennis Viewing Application,Anal
7、yze,review and browse a tennis matchSpace-filling/treemap-like hierarchy representation for a competition treeShows match,sets,games,pointsUses lenses to show shot patternsRed/green to encode two playersComposite colors on top of each other,Jin and Banks 97,14,Visualization Make-up,Match,Composite,G
8、ames,Set,15,Simulated Match Results,Game results,Lens showingball movement onindividual points,Match view,Bond won,Set results,16,Internet News Groups,Fiore&SmithMicrosoft,NetScan,17,Treemap Affordances,Good representation of two attributes beyond node-link:color and areaNot as good at representing
9、structureWhat happens if its a perfectly balanced tree of items all the same size?Also can get long-thin aspect ratiosBorders help on smaller trees,but take up too much area on large,deep ones,18,Aspect ratios,These kinds of rectangles are visually unappealing,Which has bigger area?,19,Variation,Can
10、 rectangles be made more square?think about itIn general,a very hard problem!,20,Variation:“Cluster”Treemap,SmartM Map of the MarketIllustrates stock movements“Compromises”treemap algorithm to avoid bad aspect ratiosBasic algorithm(divide and conquer)with some hand tweakingTakes advantage of shallow
11、,Wattenberg 99,Image on next slide,21,22,SmartMoney Review,Tufte-esque micro/macro viewDynamic user interface operations add to impactOne of best applications of InfoVis techniques that Ive seen,23,Other Treemap Variations,Squarified treemapBruls,Huizing,van Wijk 00Alternate approach,similar results
12、,24,Square Algorithm Problems,Small changes in data values can cause dramatic changes in layoutOrder of items in a group may be important,25,New Square Algorithms,Pivot-by-size and pivot-by-middle,Shneiderman&Wattenberg 01,Partition area into 4 regionsPick pivot element Rp Size:Largest element Middl
13、e:Middle elementR1-elements earlier in list than pivotR2-elements in list before R3 and also that makes Rp have aspect ratio closest to 1,26,Comparing the Squares,www.columbia.edu/mmw111/treemap/,Martin Wattenbergsapplet comparingdifferent methods1)aspect ratio2)structural change-metric they designe
14、d to measure movements of items-,27,New Variation,Strip treemap,Use strips to place itemsPut new rectangle into stripIf it makes average aspect ratio of all rectangles in strip go down,keep it thereIf it makes aspect ratio go up,put it back and move to next strip,28,Compare results,www.cs.umd.edu/hc
15、il/treemaps/java_algorithms/LayoutApplet.html,Compare slice and dice squarified strip pivottechniques by aspect ratio structural change readabilityReadability is metric basedon changes in direction ofeye gaze as items scanned,29,Slice-and-dice,Cluster,Squarified,Strip,Pivot-by-size,Pivot-by-middle,3
16、0,Showing Structure,Regular borderless treemap makes it challenging to discern structure of hierarchy,particularly large onesSupplement Treemap viewChange rectangles to other forms,31,Variation:Cushion Treemap,Add shading and textureto help convey structureof hierarchy,Van Wijk 99,32,SequoiaView,www
17、.win.tue.nl/sequoiaview/,File visualizerbuilt using cushion treemapnotion,33,The World of Treemaps,www.cs.umd.edu/hcil/treemaps/,Workshop in2001 there ontopic,Maryland HCILwebsite devotedto Treemaps,34,Another Technique,What if we used a radial rather than a rectangular space-filling technique?We sa
18、w node-link trees with root in center and growing outward already.Make pie-tree with root in center and children growing outwardRadial angle now corresponds to a variables rather than area,35,Appears in:American Heritage Dictionary,3rd Ed.Houghton Mifflin,1992,36,Radial Space-Filling,ChuahAndrews&He
19、ideggerInfoVis 98,37,SunBurst,38,SunBurst,Root directory at center,each successive level drawn farther out from centerSweep angle of item corresponds to sizeColor maps to file type or ageInteractive controls for moving deeper in hierarchy,changing the root,etc.Double-click on directory makes it new
20、root,39,Empirical Study,Compared SunBurst to Treemap(borderless)on a variety of file browsing tasksSunBurst performed as well(or better)in task accuracy and timeLearning effect-Performance improved with Treemap on second sessionStrong subjective preference(51-9)for SunBurstParticipants cited more ex
21、plicit depiction of structure as an important reason,Stasko,Catrambone,Guzdial&McDonaldInternational Journal of Human-Computer Studies,2000,More to come on evaluation.,40,SunBurst Negative,In large hierarchies,files at the periphery are usually tiny and very difficult to distinguish,examples,41,Fix:
22、Objectives,Make small slices biggerMaintain full circular space-filling ideaAllow detailed examination of small files within context of entire hierarchyDont alter ratios of sizes,Avoid use of multiple windows or lots of scrollbarsProvide an aesthetically pleasing interface in which it is easy to tra
23、ck changes in focus,42,3 Solutions,Three visualization+navigation techniques developed to help remedy the shortcomingAngular detailDetail outsideDetail inside,43,Angular Detail,Most“natural”Least space-efficient Most configurable by user,44,Detail Outside,Exhibits non-distorted miniature of overview
24、 Somewhat visually disconcerting Focus is quite enlarged(large circumference and 360)Relatively space efficient,45,Detail Inside,Perhaps least intuitive and most distorting Items in overview are more distinct(larger circumference)Interior 360 for focus is often sufficient,46,Key Components,Two ways
25、to increase area for focus region:larger sweep angle and longer circumferenceSmooth transitions between overview and focus allow viewer to track changesAlways display overviewAllow focus selections from anywhere:normal display,focus or overview regions,47,Potential Follow-on Work,Multiple fociVaryin
26、g radii for different levels in hierarchyUse quick-keys to walk through neighboring filesSmarter update when choosing new focus region from existing focusFourth method:expand angle of focus in place by compressing all others,48,Hybrid Approaches,Mix node-link and space-filling,49,CHEOPS,CHEOPS:A Com
27、pact Explorer For Complex HierarchiesCRIMs Hierarchical Engine for OPen Search,Beaudoin,Parent,Vroomen,96,50,What CHEOPS Is,Compressed visualization of hierarchical data,using triangle tessellationMost or all of the hierarchy can be displayed at onceSince no Degree-of-Interest(DOI)function required,
28、no major recalculation required when focus changes,51,Triangle Tessellation,Overlap/tile the trianglesThe visual object 5 is“overloaded”with the logical nodes E and FInsert overlapping triangles between logical nodes,www.crim.ca/hci/cheops/compress.html,52,What Tessellation Does,CHEOPS reuses visual
29、 components through alternate branch deploymentGrowth reduced to linear-quadratic,53,What Tessellation Does(2),To get a branch,select a node.The branch for the selected node will be“deployed”All parent nodes implicitly selected,as well.,www.crim.ca/hci/cheops/selection.html,54,Getting A Branch With
30、Reused Objects,SelectionBy selecting a node,the user sets a“reference state”in the hierarchyPre-selectionAs the cursor enters a triangle,the branch is highlighted,but not selectedMouse-click to cycle through branches,Pre-selection of Evolution,Deployment of Natural Sciences,55,Uses for CHEOPS,Overvi
31、ewwww.crim.ca/hci/cheops/index1.htmlCool Family Tree appletwww.crim.ca/ipsi/cheops/Family.html,56,Summary,Node-link diagrams or space-filling techniques?It depends on the properties of the dataNode-link typically better at exposing structure of information structureSpace-filling good for focusing on one or two additional variables of cases,57,References,Spence and CMS textsAll referred to papers,
