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# Visual Revelations: Graphical Tales of Fate and Deception from Napoleon Bonaparte to Ross Perot

by Howard Wainer, 1997, Springer-Verlag, New York, 180 p.

This book's title sounded interesting, as I am always looking for new and better ways to display data.  I was not disappointed. This is a larger-format book, comprised of many illustrations, and suitable for display on a coffee table.

Howard Wainer is a Principal Research Scientist at Educational Testing Service.  He was awarded their Senior Scientist Award in 1990 and was selected for the Lady Davis Prize. Visual Revelations is his tenth book.

Beginning with Egyptian maps around 3800 B.C., diagrams have long been used to represent data. Many of the currently popular graphical forms are credited to William Playfair (1759-1923), a draftsman employed by James Watt and brother of well-known scientist John Playfair.

The many gems include:

• Squaring the eyeball trick: deceiving the viewer by using a figure where height represents the value but visually has area proportional the the square of the height.  This perception is further amplified if the object is really 3-dimensional (e.g., beer kegs), so a figure twice as high would have 3 times the comparable volume.
• Stem-and-leaf diagrams showing two population sets measured against a common axis.   For example, the axis may measure per capita income.  One side can show state names placed at state median income, and the other side can show country names placed at their median incomes.
• Data on space shuttle o-ring failures vs. temperature provide an obvious (unfortunately post-Challenger) indication of likely failure at low temperatures.
• Charles Joseph Minard's famous plot of Napoleon's Russian Campaign.  The map shows the path of the troop movements in and out of Russia.  The width of the swath is proportional to the number of troops.  422,000 men started in June of 1812, and only 10,000 survived and returned as the year ended.
• The story of how "rose" diagrams were used by Florence Nightingale.   She applied these diagrams in 1857 to present a report on the mortality of the British Army.  A rose diagram is at first glance appears similar to a pie diagram.   Equal-angle sections represent data sets, such as time periods.  The area of sections swept represents volume.
• Rose diagrams can also be prepared such that the angle represents a data value, such as direction, and the radius represents another, dependent value.
• Constant dollar graph paper that incorporates an historical inflation index.

The book concludes with suggestions for better text composition, embedding graphics and text, and making presentation slides.

—John Schuyler, January 1998.