Representing Data - Data Points: Visualization That Means Something - page 458

What do you get when you use a polar coordinate system with the area as the
visual cue, a percentage scale on the radius, and a time scale on the rotation?
That's a polar area diagram. The most famous one, as shown in Figure 3-22,
is Florence Nightingale's chart that visualizes deaths from treatable diseases
over time.
On the Origin of Species: The Preservation of Favoured Traces , by designer and
developer Ben Fry, uses color and length, Cartesian coordinates, and a linear
scale, as shown in Figure 3-23. The interactive and animated visualization shows
how Charles Darwin's theory of evolution changed through six editions. The
gray blocks represent the original text, and each subsequent color represents
a revision in an edition, so you can see what changed and by how much.
FIGURE 3-22 Diagram of the Causes of Mortality in the Army in the East (1858) by Florence Nightingale