Saturday, November 7, 2009

Envisioning Information

Envisioning Information
My review

Passionate exposition on effective visualizations. Key takeaways are small-multiples, use of color, and use of details.
However, while mostly good, it is also distractedly didactic.
While a must-have in any collection on data visualizations, for people looking for only one book on effective data visualizations, this is not it.
This book is the poetry of visualizations; you will need to supplement it with books that are the prose of visualizations.
3 Stars???
I initially gave this book four stars, but then changed it to three stars. This may seem harsh, but hear me out. There is lots that is good in the book. However, this book's focus is more on cartography and maps. And this is where it falls short. It does not address the issue of map based visualizations in any sort of depth. Not much space is devoted to the different types of map based visualizations - dot plots, qualitative and quantitative choropleths (color patches), heatmaps, proportional bars, 3D maps, maps with variable sized markers, isopleths, flow maps, dot-location maps, graduated symbol maps, and much, much, more. The other reason for deducting two stars is the fact that this book, in 2009, does read a bit dated. It is a beautifully laid out book, that almost falls into the coffee-table book category, but looking beyond that, the material does show its age. 10 or 15 years ago the rating would have been 4 or 5 stars. Perhaps unfair on my part...

Excerpts from the book:
"All communication between the readers of an image and the makers of an image must now take place on a two-dimensional surface. Escaping this flatland is the essential task of envisioning information." [page 12]

Given the inherent multi-dimensionality of data (a measure that represents value or values over time, region, and other dimensions - e.g. number of employees by year, by country, and by line-of-business), Tufte states that we should
"... increase (1) the number of dimensions that can be represented on plane surfaces and (2) the data density (amount of information per unit area)." [page 13]

This focus on data density finds resonance throughout the book:
"Simplicity of reading derives from the context of detailed and complex information, properly arranged. A most unconventional design strategy is revealed: to clarify, add detail." [page 37]

Tufte is especially harsh on charts that feature "chart junk", what he describes as
"... display apparatus and ornamentation" that "... seek to attract and divert attention...", and that "Lurking behind chart junk is contempt both for information and for the audience. ... designing as if readers were obtuse and uncaring... " [page 33, 34]

On the topic of spatial maps, Tufte highlights a problem that may emerge with conventional choropleths (blot maps): "(they)... paint over areas formed by given geographic or political boundaries ...
" and resulting in non-uniform sizes, and "historical changes in political boundaries disrupt continuity of statistical comparisons." The solution? Or at least one solution: "Mesh maps finesse these problems." Taking the example of a map of Japan, "... the whole country of Japan was divided up in 379,000 equal-sized units and then, in a heroic endeavor, census data and addresses were collated to match the new grid squares." [page 40, 41]

"The struggle between maintenance of context and enforcement of comparison... " [page 77]

Excessive or wanton use of color can be very damaging to the visualization. Eduard Imhof enumerates four rules of minimizing such color damage:
"First rule: Pure, bright colors or very strong colors have loud, unbearable effects when they stand unrelieved over large areas adjacent to each other, but extraordinary effects can be achieved when they are used sparingly on or between dull background tones. ...
Second rule: The placing of light, bright colors mixed with white next to each other usually produces unpleasant results..." [page 82]

Tufte lists "... the fundamental uses of color in information design: to label (color as noun), to measure (color as quantity), to represent or intimate reality (color as representation), and to enliven or decorate (color as beauty)." [page 81]

In Closing:
Consider this: while you may use other books more frequently to learn and reference when creating visualizations, charts, or dashboards, you will want to keep this book handy to remind yourself of the bigger picture and the historical context of visualizations.

© 2009, Abhinav Agarwal. All rights reserved.