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Don't mess with the scale

A book

We bring attention to a book on graphics written by Bernard Lebelle, a frequent contributor to this blog.  The book came out in France earlier this year.  The title is "Convaincre avec des graphiques efficaces sous Excel, PowerPoint ...", published by Eyrolles.  Thankfully because much of the book is visual, I don't need to know French to understand much of it.  Here, I discuss two interesting things:

On page 13, he discussed flow diagrams using the energy flow example that led to a long discussion on this blog.  He proposed using a Merimecko chart instead.

Energy

On page 89, he showed a concentric circle chart (see below).  This is a relatively simple train schedule showing the frequency of trains at each hour on each day of the week.  It looks interesting because of the allusion to the clock, except that typical clocks have twelve hours rather than 24.  I'd create a set of two charts, one for the first twelve hours, one for the second twelve.

Concentric

This sort of chart is very limited in utility but it works well here because the data is entirely categorical - one or two trains per hour, hour of day, day of week - and in addition, the relationships are very simple.  In fact, the reader/user does not need to read any trends, general patterns or estimate the size or shape of anything.  The user is performing a simple search operation, that's it.

(The innermost circle is unlabelled so it is unclear what that signifies.)

Lebelle provided an alternative on page 90, which is essentially a data table, with time on the vertical dimension and calendar date on the horizontal, and the frequency inside the cells.  This is more straightforward, less interesting.


On page 151, he mentioned the self-sufficiency test that we discussed often here.  A graph should do more than just print all the data in the data set.

Lebelle is currently Senior Manager at Deloitte, the management consulting company, and he focuses on graphical construction in Excel.  This is both a limitation and an advantage.  Excel, of course, has many imperfections (don't get me started on the new and horrid Excel).  However, Excel is still the most widely used graphing application, by fa


The book takes a perspective on charting that fits our philosophy very well.  Here is a rough summary of the contents of the book (any mistakes are mine):

chapter 1: a summary of the key features of good charts... issues such as clarity and efficiency of the message are addressed

chapter 2: historical perspective, with examples from Playfair, Minard, Nightingale, etc.  page 38 has an interesting table comparing the contributions of Bertin, Tukey, Tufte, Ware and Cleveland.

chapter 3: constructs of a chart such as axes, legends, etc.  page 43 explains the difference between "information design", "infographics", "charts" and "information visualization".  introduces chartjunk, data-ink ratio.

chapter 4: "decoding" of a chart.  Discusses optical illusions, which I also consider to be fundamental to understanding the effect of charts on the audience.  Talks about how different ways of displaying the same data is perceived differently.  Interesting section (starting p.101) considering some quantitative theories about perception, citing Ernst Weber and Stanley Smith Stevens.

chapter 5: process of making a chart.  The nitty-gritty things like transforming the data, picking a scale, etc.

chapter 6: examples.  Also introduces a classification system for charts.  It has one of those flowcharts which is supposed to allow someone to pick a type of chart based on whether the data is numeric or categorical, etc.  I know this is very popular in engineering and scientific textbooks but I have never found any use for such flowcharts.  There are 30 - 40 pages of charts here and a great resource to get some ideas.

chapter 7: exercises

chapter 8: resources


Comments

Gorky

will there be an English translation be available in the near futur

David S

I strongly agree with Lebelle's use of the 24 hour time period vs. two 12 hour time periods; the allusion is less to a clock than to the cyclical nature of time. Breaking up the information into 2 pieces doesn't make sense to me.

Possibly it could be improved by a bar connecting 0:00 across the concentric circles, to guide the eye when looking at the period from (e.g.) Friday evening into Saturday morning.

ZBicyclist

Don't they use a 24 hour time metric in France? (so 5 p.m. is 17:00)

Kaiser

Now I want to know... what does a clock look like in places that use the 24-hour system? Does it use the numbers 1 to 12? Maybe just twelve stripes?

Anastasia Clarkson

Looks intriguing. I would be very interested in an English translation.

Monkey D Lueffy

I agree with ZBicyclist. In France we very often use a 24 hour time metric in most of our digital time display. I think we are not very used to the am and pm signification, that leads to frequent misunderstandings. That is why we prefer the non-confusing 24 hours system. But our analogical time display are like everywhere else 12 stripes display.

The kind of time display Lebelle showed in the books is used for a very long time in history even in cultures such as aztec reminding me the famous aztec calendar (sunstone) where circles are used for years and months.

I think the unlabelled innercircle is for public holiday which are like a national sport in france especially in french railway (source of the graphic). I just would like to add something about the reading of the graphic. Most of graphics are culturally read from top to bottom. But in this graphic, the top is given to the less important values, that is the night trains. The critical period (8 am 6pm) is kind of forgotten in the bottom. Maybe 3 levels of grey would be enough, as the third level (2 trains) adds some confusion in the reading in my opinion.

Bernard Lebelle

Kaiser, thanks for the review and glad that you've enjoyed it.

Gorky & Anastasia Clakson, translating the book in English has been an option considered with my editor but not defined date so far. You should find the french version on Amazon.

Monkey D Lueffy, what seem to be an unlabeled inner circle was actually train frequency during a railway strike June 10th 2008. Seems the connecting line to the label on the right hand side has slipped through printing checks. Will have it corrected in the future. As to where to start a 24h clock diagram, we could have zero being at the bottom and therefore having "heavy" hours 8am & 6 pm respectively on the left and right of the graphic.

David S, great idea on connecting 0:00 accross the concentrice circles - will have a go at it.

For those who dare to follow some posts in French, I've set-up a dedicated blog www.impactvisuel.net that further diggs into efficient graphs, data visualisation & business dashboard.

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