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Introduction to Graphical Presentation

Introduction to Graphical Presentation. Andy Wang CIS 5930-03 Computer Systems Performance Analysis. The Art of Graphical Presentation. Reference Works Types of Variables Guidelines for Good Graphics Charts Common Mistakes in Graphics Pictorial Games Special-Purpose Charts.

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Introduction to Graphical Presentation

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  1. Introduction toGraphical Presentation Andy Wang CIS 5930-03 Computer Systems Performance Analysis

  2. The Art of Graphical Presentation • Reference Works • Types of Variables • Guidelines for Good Graphics Charts • Common Mistakes in Graphics • Pictorial Games • Special-Purpose Charts

  3. Useful Reference Works • Edward R. Tufte, The Visual Display of Quantitative Information, Graphics Press, Cheshire, Connecticut, 1983. • Edward R. Tufte, Envisioning Information, Graphics Press, Cheshire, Connecticut, 1990. • Edward R. Tufte, Visual Explanations, Graphics Press, Cheshire, Connecticut, 1997. • Darrell Huff, How to Lie With Statistics, W.W. Norton & Co., New York, 1954

  4. Types of Variables • Qualitative • Ordered (e.g., modem, Ethernet, satellite) • Unordered (e.g., CS, math, literature) • Quantitative • Discrete (e.g., number of terminals) • Continuous (e.g., time)

  5. Charting Basedon Variable Types • Qualitative variables usually work best with bar charts or Kiviat graphs • If ordered, use bar charts to show order • Quantitative variables work well in X-Y graphs • Use points if discrete, lines if continuous • Bar charts sometimes work well for discrete

  6. Guidelines for Good Graphics Charts • Principles of graphical excellence • Principles of good graphics • Specific hints for specific situations • Aesthetics • Friendliness

  7. Principlesof Graphical Excellence • Graphical excellence is the well-designed presentation of interesting data: • Substance • Statistics • Design

  8. Graphical Excellence (2) • Complex ideas get communicated with: • Clarity • Precision • Efficiency

  9. Graphical Excellence (3) • Viewer gets: • Greatest number of ideas • In the shortest time • With the least ink • In the smallest space

  10. Graphical Excellence (4) • Is nearly always multivariate • Requires telling truth about data

  11. Principles of Good Graphics • Above all else show the data • Maximize the data-ink ratio • Erase non-data ink • Erase redundant data ink • Revise and edit

  12. Above All ElseShow the Data

  13. Above All ElseShow the Data

  14. Maximize theData-Ink Ratio

  15. Maximize theData-Ink Ratio

  16. Erase Non-Data Ink

  17. Erase Non-Data Ink North West East

  18. Erase Redundant Data Ink North West East

  19. Erase Redundant Data Ink North West East

  20. Revise and Edit

  21. Revise and Edit

  22. Revise and Edit

  23. Revise and Edit

  24. Revise and Edit

  25. Revise and Edit

  26. Revise and Edit

  27. Specific Things to Do • Give information the reader needs • Limit complexity and confusion • Have a point • Show statistics graphically • Don’t always use graphics • Discuss it in the text

  28. Give Informationthe Reader Needs • Show informative axes • Use axes to indicate range • Label things fully and intelligently • Highlight important points on the graph

  29. Giving Informationthe Reader Needs

  30. Giving Informationthe Reader Needs

  31. Limit Complexityand Confusion • Not too many curves • Single scale for all curves • No “extra” curves • No pointless decoration (“ducks”)

  32. Limiting Complexityand Confusion

  33. Limiting Complexityand Confusion

  34. Have a Point • Graphs should add information not otherwise available to reader • Don’t plot data just because you collected it • Know what you’re trying to show, and make sure the graph shows it

  35. Having a Point • Sales were up 15% this quarter:

  36. Having a Point

  37. Having a Point

  38. Having a Point

  39. Show Statistics Graphically • Put bars in a reasonable order • Geographical • Best to worst • Even alphabetic • Make bar widths reflect interval widths • Hard to do with most graphing software • Show confidence intervals on the graph • Examples will be shown later

  40. Don’t AlwaysUse Graphics • Tables are best for small sets of numbers • Tufte says 20 or fewer • Also best for certain arrangements of data • E.g., 10 graphs of 3 points each • Sometimes a simple sentence will do • Always ask whether the chart is the best way to present the information • And whether it brings out your message

  41. Text Would HaveBeen Better

  42. Discuss It in the Text • Figures should be self-explanatory • Many people scan papers, just look at graphs • Good graphs build interest, “hook” readers • But text should highlight and aid figures • Tell readers when to look at figures • Point out what figure is telling them • Expand on what figure has to say

  43. Aesthetics • Not everyone is an artist • But figures should be visually pleasing • Elegance is found in • Simplicity of design • Complexity of data

  44. Principles of Aesthetics • Use appropriate format and design • Use words, numbers, drawings together • Reflect balance, proportion, relevant scale • Keep detail and complexity accessible • Have story about the data (narrative quality) • Do professional job of drawing • Avoid decoration and chartjunk

  45. Use AppropriateFormat and Design • Don’t automatically draw a graph • Mentioned before • Choose graphical format carefully • Sometimes “text graphic” works best • Use text placement to communicate numbers • Very close to being a table

  46. CEA: +4.7 WEF: 6.8 DR: +4.5 CB: 6.7 NABE: +4.5 NABE: 6.7 WEF: +4.5 IBM: 6.6 CBO: +4.4 DR: 6.5 CB: +4.2 NABE: +6.2 CBO: 6.3 IBM: +4.1 IBM: +5.9 WEF: +21 CEA: 6.3 GNP: +3.8 IPG: +5.8 CPI: +7.7 Profits: +13.3 Unempl: 6.0 CE: +2.9 CB: +5.5 IBM: +6.6 DR: +10.5 DR: +5.2 NABE: +6.5 IBM: +10.4 WEF: +4.8 CB: +6.2 CE: +6.5 Using Text as a Graphic About a year ago, eight forecasters were asked for their predictions on some key economic indicators. Here’s how the forecasts stack up against the probable 1978 results (shown in the black panel). (New York Times, Jan. 2, 1979)

  47. The Stem-and-Leaf Plot • From Tukey, via Tufte, heights of volcanoes in feet:0|98766562 1|97719630 2|99987766544422211009850 3|876655412099551426 4|9998844331929433361107 5|97666666554422210097731 6|898665441077761065 7|98855431100652108073 8|653322122937

  48. Choosinga Graphical Format • Many options, more being invented all the time • Examples will be given later • See Jain for some commonly useful ones • Tufte shows ways to get creative • Choose a format that reflects your data • Or that helps you analyze it yourself

  49. Use Words, Numbers, Drawings Together • Put graphics near or in text that discusses them • Even if you have to murder your word processor • Integrate text into graphics • Tufte: “Data graphics are paragraphs about data and should be treated as such”

  50. Reflect Balance, Proportion, Relevant Scale • Much of this boils down to “artistic sense” • Make sure things are big enough to read • Tiny type is OK only for young people! • Keep lines thin • But use heavier lines to indicate important information • Keep horizontal larger than vertical • About 50% larger works well

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