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Chartjunk and Graphics Integrity

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Tricking the reviewer with design variation is to use areas to show 1D data. Lie factor: 2.8 ... Show data variation, not design variation ... – PowerPoint PPT presentation

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Title: Chartjunk and Graphics Integrity


1
Chartjunk and Graphics Integrity
  • Han-Wei Shen
  • CSE 788.14K
  • Winter 2007

2
Types of chartjunk
  • Chartjunk are non-data-ink or redundant data-ink
    decoration
  • Unintended Optical Art (Moiré vibration)
  • The Grid
  • The Duck Self-promoting Graphics

3
Unintended Optical Art
  • Mainly rely on moiré effects
  • Distracting appearance of vibration and movement
  • The most common form of graphical clutter

4
Moiré Vibrations
5
Streamline Placement
6
The Grid
  • Dark grid lines are chartjunk
  • The grid should usually be muted or completely
    supressed

7
The Grid (contd)
  • Mareys train schedule

8
The Duck
  • Self-promoting graphics when the data measures
    become design elements

9
Duck Examples
10
Graphical Integrity
  • Graphical excellence begins with telling the
    truth about the data

Some examples of Lie
11
Two Principles
  • The representation of numbers, as physically
    measured on the surface of the graphics, should
    be directly proportional to the numerical
    quantities represented
  • Clear, detailed and thorough labeling should be
    used to defeat distoration

12
Violating rule 1
18 miles/gallon 0.6 inches 27.5miles/gallon
5.3 inches
13
Lie Factor
  • Rule 1 can be measured by Lie factor
  • size of effect shown in
    graphics
  • size of effect in
    data
  • Lie Factor equal to one is ideal
  • The previous slide has a lie factor of 14.8

Lie Factor
14
Design and Data Variation
  • Show data variation, not design variation
  • 1973-1978 one vertical inch
  • equals to 8.00. In 1979,
  • One vertical inch equals 3-4
  • 1973-1978 one horzontal inch
  • equals 3.7 years, while 1979
  • equals 0.57 year

15
Example
  • Lie factor 9.5
  • The price of oil is
  • inflated so need to be repaired.

16
Government Spending
  • Tricks to exaggerate the growth of spending

17
Real Government Spending
  • Tricks to exaggerate the growth of spending
  • Tricks to exaggerate the growth of spending

18
Visual Area and Numerical Measure
  • Tricking the reviewer with design variation is to
    use areas to show 1D data

Lie factor 2.8
19
Content is Essential
  • Graphics must not quote data out of context

20
Content is Essential
  • Graphics must not quote data out of context

21
The principles
  • The representation of numbers, as physically
    measured on the surface of graphics, should be
    proportionally to the numerical quantities
    represented
  • Use clear and detailed labeling
  • Show data variation, not design variation
  • The number of information-carrying dimensions
    depicted should not exceed the number of
    dimensions in the data
  • Graphics should not quote data out of context

22
Why do graphics lie?
  • Lack of quantitative skills of professional
    artists
  • The doctrine that statistical data are boring
  • The doctrine that graphics are only for the
    unsophisticated readers
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