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SIMS 247 Lecture 3 Graphing Basics, Continued

SIMS 247 Lecture 3 Graphing Basics, Continued. January 27, 1998. Today. Finish graphing basics Demonstrate on web access example Discuss Tufte’s Data Ink Maximization principle. Types of Symbolic Displays (Kosslyn 89). Graphs Charts Maps Diagrams. Types of Symbolic Displays. Graphs

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SIMS 247 Lecture 3 Graphing Basics, Continued

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  1. SIMS 247 Lecture 3Graphing Basics, Continued January 27, 1998 Marti Hearst SIMS 247

  2. Today • Finish graphing basics • Demonstrate on web access example • Discuss Tufte’s Data Ink Maximization principle Marti Hearst SIMS 247

  3. Types of Symbolic Displays(Kosslyn 89) • Graphs • Charts • Maps • Diagrams Marti Hearst SIMS 247

  4. Types of Symbolic Displays • Graphs • at least two scales required • values associated by a symmetric “paired with” relation • Examples: scatter-plot, bar-chart, layer-graph • Charts • discrete relations among discrete entities • structure relates entities to one another • lines and relative position serve as links • Examples: family-tree, flow-chart, network diagram Marti Hearst SIMS 247

  5. Types of Symbolic Displays (cont.) • Maps • internal relations determined (in part) by the spatial relations of what is pictured • labels paired with locations • Examples: map of census data, topographic maps • Diagrams • schematic pictures of objects or entities • parts are symbolic (unlike photographs) • Examples: how-to illustrations, figures in a manual Marti Hearst SIMS 247

  6. Scatter plots Line graphs Time series (strip charts) Dot plots Bar Charts Pie Charts Layer Graphs Standard Graph Types Marti Hearst SIMS 247

  7. D I Choosing the Axes • Independent vs. Dependent variables • the dependent variable changes relative to the independent one • sales against season • tax revenue against city • What happens when there is more than one independent variable? • Most important is assigned to X axis • Other(s) differentiated by mark symbol Marti Hearst SIMS 247

  8. Basic Types of Data • Qualitative -- nominal • no inherent order (for comparisons) • city names, types of diseases, ... • Qualitative -- ordinal • ordered, but not at measurable intervals • first, second, third, … • cold, warm, hot • Quantitative -- interval and ratio Marti Hearst SIMS 247

  9. Combining Data Types in Graphs(adapted from Kosslyn 89) Nominal by Nominal: Use a Chart Marti Hearst SIMS 247

  10. Scatter Plots • Qualitatively determine if variables • highly correlated • linear mapping between horizonal & vertical axes • nonlinear relationship • a curvature in the pattern of plotted points • low correlation • spherical, rectangular, or irregular distributions • Place points of interest in context • apply shapes or color to points representing special entities, see where they end up Marti Hearst SIMS 247

  11. Time Series • Change over time • Facilitates finding trends • Also known as “strip charts” Marti Hearst SIMS 247

  12. Web Page Visit Behavior • What are our goals? • What questions do we want to answer? • What kind of data might we collect? • How might we convey this information? • Who is the audience? Marti Hearst SIMS 247

  13. Web Access Data Types(consider the possible combinations) Marti Hearst SIMS 247

  14. length of page length of access Hypothetical Graphs # of accesses # of accesses length of access URL url 1 url 2 url 3 url 4 url 5 url 6 url 7 45 40 35 # of accesses 30 length of access 25 20 15 10 5 0 long long very short # of accesses medium days length of page Marti Hearst SIMS 247

  15. How to Show Link Traversal? How to link together the to-links and from-links in our web access example? Marti Hearst SIMS 247

  16. Charts • Structural / organizational material • nominal by nominal • Specify relationships among discrete members of a set • Not relating on quantitative dimensions • Components of Charts(Kosslyn 89): • directed vs. undirected links • how many types of links • types of mapping e.g., one-to-one, one-to-many, many-to-many • Tables can also be considered charts Marti Hearst SIMS 247

  17. Mapping Types in Charts one-to-one one-to-many many-to-many Marti Hearst SIMS 247

  18. Chart Example(organizational chart) Marti Hearst SIMS 247

  19. Chart Example(Software architecture, labels omitted, by Chen and Hong 97) Marti Hearst SIMS 247

  20. How to show link patterns in web access example? Problem: only shows one step Think about this for next time. Marti Hearst SIMS 247

  21. Graph/Chart Hybrids • An area for innovation • Combine Structure with Graphics • Example: Docuverse (Spring et. al 96) • structure: file system structure • graphics: color -> file age • Example: TileBars (Hearst 95) • structure: document subtopics (columns) • structure: faceted query (rows) • graphics: gray-level -> number of hits Marti Hearst SIMS 247

  22. Docuverse (Spring et. al 96) Marti Hearst SIMS 247

  23. TileBars (Hearst 95) Marti Hearst SIMS 247

  24. Discussion:Tufte’s Notion of Data Ink Maximization • What is the main idea? • draw viewers attention to the substance of the graphic • the role of redundancy • principles of editing and redesign • What’s wrong with this? What is he really getting at? Marti Hearst SIMS 247

  25. Next Time:Multidimensional Graphing How do we handle cases with more than three variables? • Multiple views • Scatterplot matrix • Parallel Coordinates • Tufte examples: combine space and time • Interaction/animation across time Marti Hearst SIMS 247

  26. References for this Lecture • Kosslyn, Stephen M. Understanding Charts and Graphs. Applied Cognitive Psychology, 3, 185-226. 1989 • Spring, Michael B., Morse, Emile, and Heo, Misook. Multi-level Navigation of a Document Space. http://www.lis.pitt.edu/~spring/mlnds/nlnds/mlnds.html • Schall, Matthew. SPSS DIAMOND: a visual exploratory data analysis tool. Perspective, 18 (2), 1995. http://www.spss.com/cool/papers/diamondw.html • Hearst, M. TileBars, Visualization of Term Distirubtion in Full Text Information Access. Proceedings of ACM SIGCHI 95. • Tufte 83 Marti Hearst SIMS 247

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