Strategies For Effective Data Visualization

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Strategies for EffectiveData VisualizationAnneli JoplinNovember 8, 2017anneli@rice.edu

Visualization is inherently open-endedSizeShadeAspect idthShapeScaleMotionYX

Best practices depend on context

Approach dictates likelihood of bability of success ctive

An intentional approach to datavisualizationWhat we knowabout perceptionNew ideasto considerData visualizationdesign process

Implications of currentperception research

Vision is a multistep processLight triggers a neural signal through the optic nerveColin Ware, Information Visualization, 2004

Vision is a multistep processBrain identifies basic features first, and then analyzes furtherColin Ware, Information Visualization, 2004

Preattention“When something just catches our eye, it istapping into our earliest stages of attention.”– Stephanie Evergreen, Presenting Data Effectively9

Preattentive processing is instantaneousHow many 254869752158652321221345890011001457Preattentive processing 10 msec per itemTypical processing 40 msec per itemPattern recognitionPreattentive contrastAlberto Cairo, The Functional Art, 2013 / Colin Ware, Information Visualization, 2004

Gestalt principles of pattern recognitionThe visual brain Evolved to detect patterns Groups similar objects Separates different objects

PROXIMITYObjects close together are grouped467281276561271279948278239113576133Alberto Cairo, The Functional Art, 2013459166417183222587771186222177336993

PROXIMITYObjects close together are groupedAlberto Cairo, The Functional Art, 2013

SIMILARITYSimilar objects perceived as a groupAlberto Cairo, The Functional Art, 2013 / USA by Alexander Skowalsky for the Noun Project

Scatter bubble plot encode times in colorBubbles of various sizes are grouped via color (similarity)Forsyth Alexander, When data imitates art, www.ibm.com/blogs/business-analytics

CONNECTEDNESSLinked objects form a natural groupAlberto Cairo, The Functional Art, 2013

CONNECTEDNESSConnecting lines visually identify pairsWhich dots do yougroup and why?

CONNECTEDNESSConnecting lines visually identify pairsConnectednessrelates the two circlesfrom each category

ENCLOSUREEnclosed objects form a natural groupAlberto Cairo, The Functional Art, 2013

ENCLOSUREEnclosed objects are evaluated togetherBang Wong, Nature Methods, Vol. 7 No. 11, 2010

CLOSURETendency to perceive complete formsStephen Few, Show Me the Numbers, 2nd Edition, 2012

CLOSURETendency to perceive complete formsNo need to define area of graph completelyRedundant enclosureintroduces a distractionStephen Few, Show Me the Numbers, 2nd Edition, 2012

SYMMETRYSymmetry suggests a visual wholeColin Ware, Information Visualization, 2004

SYMMETRYButterfly plots highlight differences

CONTINUITYCurved contours imply connectionColin Ware, Information Visualization, 2004

Curved connections are easier to followWhy did we evolve to identify contours?Alberto Cairo, The Functional Art, 2013 / Colin Ware, Information Visualization, 2004ç

Curves help the viewer visually followconnections through crowded dataSocial Networks, behance.net/gallery

Gestalt summaryTake advantage of pattern recognition tendencies mmetryContinuityPattern recognitionPreattentive contrast

Range of evolved preattentive attributesTypeFormColorSpatial closureHueIntensity2D positionStephen Few, Show Me the Numbers, 2nd Edition, 2012

Alter a preattentive attribute to makesomething stand outRolandi, M. et al. Adv. Mater. 2011

Limits to distinct perceptionPreattentive processing limited to 1 attribute at a timeColor intensity onlyStephen Few, Show Me the Numbers, 2nd Edition, 2012Intensity and shape

Overwhelming repetition results in lossof meaningToo many bright colorsmeans nothing stands outMartin Krzywinski, Nature Methods, Vol. 10 No. 5 2013

Natural scenes exhibit muted colorsReserve bright colors for emphasisBrightmetrics, Using Color in Data Visualization, 2010

Above all else, show the dataTUFTEData ink ratio data inktotal ink used in the graphicThe Visual Display ofQuantitative InformationEdward Tufte, The Visual Display of Quantitative Information, 1983

Clutter distracts from preattentive cuesRemove all chartjunk, for example: Distracting patterns Gridlines Elements only for “artistic appeal”Edward R. Tufte, The Visual Display of Quantitative Information, 1983

3D effects are almost always chartjunkNils Gehlenborg and Bang Wong, Nature Methods, Vol. 9 No. 9 2012

Visually separate data from otherelementsSimilarity between theellipses and linesreduces visual contrastMartin Krzywinski, Nature Methods, Vol. 10 No. 3 2013

“Sometimes clarity demands morespace” – Stephen FewBEFORESeparating traces intotrellis display highlightstrends more effectivelyAFTER

Make emphasis more effective byeliminating excess decorationWhat would you removefrom this chart?Size Matters, rs/

Preattentive contrast summaryLimit preattentive attributes to emphasis Rely on muted colors Soften gridlines, axes, labels, etc. Remove chartjunk

Visual information requires decodingColin Ware, Information Visualization, 2004

Visual information requires decodingImplications for data visualization –1. Working memory limits number of items remembered2. Perception accuracy is distance dependent3. Accuracy of perception influenced by visuals

Keep the number of items displayed inone visualization to 4 if possible

Reduce distance between comparabledata to increase accuracyMarc Streit and Nils Gehlenborg , Nature Methods, Vol. 11 No. 2 2014

Select attribute based on purposeData typesCategoricalQuantitativeDivide informationMeasure thingsCompanyParticipantMoleculeOrder (1, 2, 3)AddressTimeCountIntensityProfit

Few attributes can encode quant. dataTypeFormColorSpatial closureHueIntensity2D positionStephen Few, Show Me the Numbers, 2nd Edition, 2012Quantitative?YesYes, but limitedNoYes, but limitedNoNoNoYes, but limitedYes

Shifts in color are not visually equivalentto changes in valueCommonly utilized color scales are not perceived accuratelyBang Wong, Nature Methods, Vol. 8 No. 3 20111

Perception of color depends onsurroundingsUse color for labeling, emphasis or when value doesn’t matterBang Wong, Nature Methods, Vol. 7 No. 8 2010

Length is perceived quantitativelyNumber and visual length are tied togetherThis works to ouradvantage in a barchart, for example

Bar charts must start at zeroLength has an inherent numerical valueScale 0 – 100Scale 60 – 100Data encoded with length is highlydistorted with a shortened scale

An alternative – the dot plot2D position does not elicit a numerical valueScale 0 – 1002D positiondoes notrequire a 0value forquantitativecomparisonScale 60 – 100

Dot plots display multiple data setsmore clearly than bar charts

Lollipop charts also compare valueswithout emphasizing lengthBar chart with lessemphasis on length

Cleveland and McGill identified 10elementary perceptual tasksWilliam Cleveland, Graphical Perception, 1984

Graphical perception attributes inorder of accuracyAllows moreaccuratejudgmentsposition along a common scaleposition along nonaligned scaleslengthangleareaAllows moregenericjudgmentsvolume*Accuracy is notalways better,just make intentionalchoices based onpurposecurvatureshading, color saturationWilliam Cleveland, The Elements of Graphing Data, 1994 / Alberto Cairo, The Functional Art

Bar charts are easier to evaluateaccurately than pie chartsPosition along common scale area or angle

Simple bar charts more accurate thanstacked barsPosition along common scale length

Use small multiples instead of stackedbars when numbers matterRetains common axis, butalso enables comparison

Curve comparisons are difficult, plotdifference insteadCurves A and BDifference (A – B)

Select an aspect ratio that places keylines close to 45 Angles around 45 areperceived accuratelySmall angles are moredifficult to assessNaomi B. Robbins, Creating More Effective Graphs, 2005

Aspect ratio affects perception of dataHow to select the aspect ratio that allows for accuratejudgment?Naomi B. Robbins, Creating More Effective Graphs, 2005

Rescale line graph segments in multiplepanels to improve angle perceptionGregor McInerny, Martin Krzywinski, Nature Methods, Vol. 12 No. 7 2015

Graphical perception summarySelect encoding attributes based on purpose Perception accuracy is distance dependent Position on a common axis perceived most accurately Bar graphs outperform pie charts Small multiples outperform stacked bars Curve perception is not accurate Angles close to 45 are evaluated most easily

Exercise 1 –Accounting for perception

How would you apply visual perceptionprinciples to improve this chart?Example curated by Melissa Clarkson, melissaclarkson.com

One solution – Bar chart trellis displayallows comparison across samplesRedesign created by Melissa Clarkson, melissaclarkson.com

How would you apply visual perceptionprinciples to improve this chart?Example curated by Melissa Clarkson, melissaclarkson.com

One solution – Dot plot allows easycomparison across conditionsRedesign created by Melissa Clarkson, melissaclarkson.com

Strategies to facilitateeffective data visualization

Field of data visualizationTUFTEThe Visual Display ofQuantitative InformationHOLMESDesigner’s Guide to CreatingCharts and Diagrams

Tufte prioritized function, Holmes formTUFTEHOLMESVSNigel Holmes, Designer’s Guide to Creating Charts and Graphs, 1984

Approach style guidelinesProbability of success intentionalapproachEffectiveIneffective

Recommended design process1. Explore data visually2. Identify visualization message3. Select a chart type and create4. Evaluate and revise5. Take advantage of templates

Recommended design process1. Explore data visually2. Identify visualization message3. Select a chart type and create4. Evaluate and revise5. Take advantage of templates

Scatter plot matrixStephen Turner, Scatterplot Matrices in R, 2011, r-bloggers.com

Streamline with a visualization dashboardPreset charts provide an instant view of new dataAlberto Cairo, thefunctionalart.com, 2017

Add interactive components to quicklyfilter and display dataAlberto Cairo, thefunctionalart.com, 2017

Exploring high dimensional dataOnline data display1. Embedding projectorProjectionRice Visualization Lab(closed for relocation)2. HypertoolsTensorFlow, Embeddings, tensorflow.org, 2017 / Andrew C. Heuser, Hypertools, 2017

Recommended design process1. Explore data visually2. Identify visualization message3. Select a chart type and create4. Evaluate and revise5. Take advantage of templates

Evaluate visualizations on bothinformative and emotive lnessIntuitivenessAestheticsEngagementVery usefulUselessAll relevant dataNo relevant dataClear and easyUnclear and difficultInaccurateAccurateUnfamiliarFamiliar, easy to readUglyDistracts from dataPleasing to the eyeNeutralStephen Few, Perceptual Edge, Visual Business Intelligence Newsletter, 2017BeautifulDraws one in

Exercise 2 –Evaluating visualizations

Example 1 – ScatterplotJonathan A. Schwabish, An Economist’s Guide to Visualizing Data, 2014

Coloring and labeling key datafacilitates interpretationJonathan A. Schwabish, An Economist’s Guide to Visualizing Data, 2014

Example 2 – Bar / dot plotJonathan A. Schwabish, An Economist’s Guide to Visualizing Data, 2014

Horizontal dot plot visually comparescategories at two points in timeJonathan A. Schwabish, An Economist’s Guide to Visualizing Data, 2014

Example 3 – Stacked bar chartCastro-Nallar, E. et al Peer J, 2015, accessed at peerj.com/articles/1140/

Recommended design process1. Explore data visually2. Identify visualization message3. Select a chart type and create4. Evaluate and revise5. Take advantage of design templates

Create templates to save timeTemplates eliminate mundane design decisionsSpreadsheets(Excel, Origin)Secondary components(Illustrator, InDesign, PowerPoint)Dashboards(Excel, Tableau)Scripts(Matlab, Python, Origin)

Resources on campusDigital Media CommonsRice Visualization LabCWOVC online resourcesGIS Data CenterCenter for ResearchComputing

Exploring the frontiersof data visualization

Less common chart types provide newmeans of data explorationSeverino Ribecca, The Data Visualization Catalogue, dataviscatalogue.com/methods/

Raw graphs – a free way to experimentwith less common visualizationsSupports conventional andunconventional chart typesrawgraphs.io

Sunburst diagramCapable of displaying hierarchies over multiple levelsUse to show subdivisionsof a multi-level structureSeverino Ribecca, The Data Visualization Catalogue, dataviscatalogue.com/methods/

Sunburst diagram applied to visualizememory usage

Butterfly plot

Deviation bar chart

Slopegraph utilizes angle to comparechange between groupsDisplays changeacross categoriesusing slopeAxes labels alsoserve as ranked listsChart from the New York Times / h/infant stats.html

Parallel coordinates showcase trendsacross dimensionsExtension of slopegraph to high dimensional dataOrder matters – place thedimensions you aim tocompare close togetherProtovis, A Graphical Toolkit for Visualization, http://mbostock.github.io/protovis/ex/cars.html

Brushing highlights relevant data rangesInteractivity allows exploration of trends in the dataSelect a category rangeRobert Kosara, Parallel Coordinates, eagereyes.org

Heat mapUse to highlightoverall data trendsSeverino Ribecca, The Data Visualization Catalogue, dataviscatalogue.com/methods/

Expanded heat map presents largescale patterns in a compact wayStatistical Computing and Graphics Newsletter, Volume 20, December 2009

Radar chartsRepresent the value of multiple variables as a polygonSeverino Ribecca, The Data Visualization Catalogue, dataviscatalogue.com/methods/

Sunburst style chart shows cyclicrelationship*good for high dimensional data*Moritz Stefaner, The Rhythm of Food, truth-and-beauty.net

Horizon chart – high dimensional areachartValue encoded incolor and intensityStephen Few, Time on the Horizon, Perceptual Edge, 2008

Horizon chart – high dimensional areachartTiers grouped toimprove perceptionof differencesStephen Few, Time on the Horizon, Perceptual Edge, 2008

Horizon chart – high dimensional areachartStephen Few, Time on the Horizon, Perceptual Edge, 2008

Horizon chart – high dimensional areachartCollapsed stackspresent compactinformationStephen Few, Time on the Horizon, Perceptual Edge, 2008

Horizon chart – high dimensional areachartHigh intensitypockets stand outStephen Few, Time on the Horizon, Perceptual Edge, 2008

Learn more at cwovc.rice.edu

Stephen Few, Perceptual Edge, Visual Business Intelligence Newsletter, 2017 . Exercise 2 – Evaluating visualizations . Example 1 – Scatterplot Jonathan A. Schwabish, An Economist’s Guide to Visualizing Data, 2014 . Coloring and labeling key data facilitates interpretation

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