Chartjunk and Graphics Integrity

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Chartjunk and Graphics Integrity

• Han-Wei Shen
• CSE 788.14K
• Winter 2007

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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

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Unintended Optical Art

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

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Moiré Vibrations
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Streamline Placement
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The Grid

• Dark grid lines are chartjunk
• The grid should usually be muted or completely
  supressed

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The Grid (contd)

• Mareys train schedule

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The Duck

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

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Duck Examples
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Graphical Integrity

• Graphical excellence begins with telling the
  truth about the data

Some examples of Lie
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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

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Violating rule 1
18 miles/gallon 0.6 inches 27.5miles/gallon
5.3 inches
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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
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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

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Example

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

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Government Spending

• Tricks to exaggerate the growth of spending

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Real Government Spending

• Tricks to exaggerate the growth of spending

• Tricks to exaggerate the growth of spending

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Visual Area and Numerical Measure

• Tricking the reviewer with design variation is to
  use areas to show 1D data

Lie factor 2.8
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Content is Essential

• Graphics must not quote data out of context

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Content is Essential

• Graphics must not quote data out of context

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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

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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