“It may well be the best statistical graphic ever drawn.”

On a recommendation from XKCD, I picked up a copy of The Visual Display of Quantitative Information by Edward R. Tufte. So far it’s been a surprisingly interesting read, and I recommend it to anyone who likes graphs.

It also features an image that was discussed in my technical writing class last year. It is Charles Minard’s graphic documenting Napoleon’s disastrous attempt at invading Russia in 1812:

minard-resize
minard-resize

Now before your eyes glaze over, hear me out on this. First, I highly recommend clicking the image for a larger version courtesy of Wikipedia. This graphic tells a story far more succinctly than any history book. The top part is a map of Russian territory. The width of the tan line represents the number of troops as they march toward Moscow. The French army started its campaign with 422,000 troops as it crossed the Niemen river. Twenty-two thousand shortly split off to guard the rear as the rest of the army marched through what is now Lithuania. Another contingent separated from the main group to guard the flank. By the time Napoleon reached Moscow, he was left with only one quarter of his original forces.

The retreat, which started in October, is where the graph gets really interesting. In addition to the black line plotting the location and number of the French troops, the scale at the bottom displays dates and temperatures as the army trudged home through the Russian winter. In early December, as the army was nearing the end of its reatreat, temperatures dropped to -30 degrees Reaumur, about -35 Fahrenheit. By the time Napoleon crossed back over the Niemen, his nearly half-million-strong army was reduced to 10,000 troops.

I’m in no way a history geek, but I’m still fascinated by the story Minard tells using only quantitative facts. In his book, Tufte points out that six variables are expressed in the graphic: two dimensions of space, number of troops, direction of troop movement, time, and temperature. He declares, “It may well be the best statistical graphic ever drawn.” I think I’ve got to agree.