Tip of the Week #32
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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
- 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.
Copyright © 1998 by John R. Schuyler. All rights reserved. Permission to copy with
reproduction of this notice.