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Displaying Quantitative Information

Displaying Quantitative Information. An exploration of Edward R. Tufte’s The Visual Display of Quantitative Information. Jeffrey Nichols Programming Usable Interfaces May 2, 2003. Good graphics. Napolean’s invasion of Russia, as drawn by Charles Joseph Minard (1781-1870).

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Displaying Quantitative Information

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  1. Displaying Quantitative Information An exploration of Edward R. Tufte’s The Visual Display of Quantitative Information Jeffrey Nichols Programming Usable Interfaces May 2, 2003

  2. Good graphics Napolean’s invasion of Russia, as drawn by Charles Joseph Minard (1781-1870)

  3. More good graphics The price of wheat compared to labour wages, William Playfair (1759-1823)

  4. More good graphics French train schedule, as drawn by E.J. Marey (1830-1904)

  5. More good graphics Map of the northern galactic hemisphere (1.3 million galaxies shown)

  6. What made these graphics good?

  7. Bad graphics

  8. More bad graphics

  9. More bad graphics

  10. More bad graphics

  11. More bad USA Today Graphs

  12. What made these graphics bad?

  13. How can we make better graphics? Tufte presents some principles of data graphics • Above all else, show the data. • Maximize the data-ink ratio • Erase non-data-ink • Erase redundant data-ink • Revise and edit

  14. Above all else, show the data

  15. Show the data

  16. Data-Ink • Ink that changes as the data changes • Non-redundant ink!

  17. Data-Ink Ratio data-ink Data-ink ratio = Total ink used to print graphic = Proportion of a graphic’s ink devoted to the non-redundant display of data-information. = 1.0 – proportion of graphic that can be erased without the loss of information

  18. What is the data-ink ratio of this graphic? Ratio of Histogram < 0.05 !!!

  19. Ratio of USA Today Graphic • What is the data-ink ratio of this graphic? < 0.001

  20. How can we make better graphics? Tufte presents some principles of data graphics • Above all else, show the data. • Maximize the data-ink ratio • Within reason • Every bit of ink on a graphic requires a reason • Erase non-data-ink • Erase redundant data-ink • Revise and edit

  21. How can we make better graphics? Tufte presents some principles of data graphics • Above all else, show the data. • Maximize the data-ink ratio • Erase non-data-ink • Erase redundant data-ink • Revise and edit

  22. Erase non-data-ink, within reason

  23. Erase non-data-ink, within reason

  24. Erase non-data-ink, within reason 11 5 2 1 0 18 7 Histogram of Midterm Results # of Students A- B+ A B B- C Scoring Buckets

  25. Erase redundant data-ink 11 5 2 1 0 18 7 Histogram of Midterm Results # of Students A- B+ A B B- C Scoring Buckets

  26. Erase redundant data-ink 18 11 5 2 1 0 7 Histogram of Midterm Results What’s the data-ink ratio? # of Students A- B+ A B B- C Scoring Buckets

  27. How can we make better graphics? Tufte presents some principles of data graphics • Above all else, show the data. • Maximize the data-ink ratio • Erase non-data-ink • Erase redundant data-ink • Revise and edit

  28. The Principles Applied to Common Forms Box Plots Maximum 75% Median 25% Minimum

  29. The Principles Applied to Common Forms Box Plots Maximum 75% Median 25% Minimum

  30. The Principles Applied to Common Forms Bar Graphs Modified Graph Original Graph

  31. The Principles Applied to Common Forms Scatter Plots Modified Graph Original Graph

  32. The Principles Applied to Common Forms Another Scatter Plot Variant

  33. Conclusions • Show data variation, not design variation • Avoid using ink for non-data items • Avoid redundancy • Clear and detailed labeling should be used to defeat graphical distortion • Revise and Edit

  34. Questions?

  35. Thanks for a great class! Reminder: Final Exam on Friday, May 9th at 8:30am in this room

  36. More Bad USA Today Graphs

  37. Tufte’s Principles • Graphical Integrity • The representation of numbers, as physically measured on the surface of the graphic itself, should be directly proportional to the numerical quantities represented. • Clear, detailed, and thorough labeling should be used to defeat graphical distortion and ambiguity. Write out explanations of the data on the graphic itself. Label important events in the data. • Show data variation, not design variation. • In time-series displays of money, deflated and standardized units of monetary measurement are nearly always better than nominal units. • The number of information-carrying (variable) dimensions depicted should not exceed the number of dimensions in the data. • Graphics must not quote the data out of context. • Theory of Data Graphics • Above all else, show the data. • Maximize the data-ink ratio • Erase non-data-ink • Erase redundant data-ink • Revise and edit • Other comments • Graphical elegance is often found in simplicity of design and complexity of data • Data graphics are paragraphs about data and should be treated as such

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