01 November 2009

Visual Explanations

Edward Tufte's Visual Explanations is a complement to his earlier works The Visual Display of Quantitative Information and Envisioning Information (neither of which I have read).

Engineers like myself may benefit most from the first few chapters, in which Tufte presents case studies that demonstrate the importance of data representation in statistical graphics. Whether the graphics obscure or reveal cause/effect can mean the difference between life (as when John Snow identified tainted well water as the cause of the London cholera epidemic of 1854) and death (as when NASA made the catastrophic decision to launch the space shuttle Challenger in cold weather on 28 January 1986). Tufte calls attention to some important issues in data presentation, but I think his criticism of the NASA engineers is not really justifiable (hindsight being 20/20 and all).

Visual Explanations is ostensibly about showing cause and effect graphically, but there are many nuggets throughout that apply to informational graphics more generally. Tufte gives a suite of graphical "design patterns" that are good to keep in mind: eliminating unnecessary clutter, facilitating direct comparisons, using the right amount of contrast, and so on.

The later sections of the book have less specific practical advice but plenty of striking images. The last chapter focuses on the idea of a "visual confection" (Tufte's terminology, I believe)— an image, frequently fanciful, synthesized from smaller images or parts, that tells a coherent story. Perhaps the most poignant of these is the public safety message from The Washington Post, "Why is the Potomac River So Dangerous?", which was later reproduced on a metal sign next to the river.

One takeaway is the notion that a printed graphic is often much more illuminating than a photograph. A photograph can only show you what something looks like. But a cutaway, schematic, or other illustration can show you how something is, by virtue of calling attention to the important details, suppressing the unimportant ones, and indicating cause/effect or the passage of time. Illustrations are an effective and efficient way of conveying an idea directly to the mind's eye.

The book itself is an examplar of the strategies that Tufte advocates. Illustrations appear inline or near where they are referenced in the text. There are no awkward page breaks that require the reader to flip back and forth between an illustration and the text that describes it. The case studies are bite-sized and easy to digest.

Recommended, and an easy read.

This is one of those books that colors one's perception of the world. For example, I can't help but think that some Google Maps engineers took some of Tufte's advice to heart in their recent visual redesign. Many of the maps styles are now more harmonious and suppress unneeded detail and distractions.

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