Visualizing with Clarity - Data Points: Visualization That Means Something - page 552

For example, Figure 5-8 shows a number of identified species of invertebrates
and vertebrates. The bar chart on the left and the bubble chart on the right
show the same data, but because there so many more identified species of
insects than vertebrates, the bars for the latter are dwarfed. They are barely
visible, and the bar for corals is also just a sliver.

On the other hand, the bubbles let you put large and small counts in the same
space. The downside is that you can't visually compare values as accurately
as a bar chart, but in this case, the bar chart doesn't even give you a chance
to compare the values. So there's a trade-off.

Note: Area can also make data seem more tan-
gible or relatable, because physical objects take
up space. A circle or a square uses more space
than a dot on a screen or paper. There's less
abstraction between visual cue and real world.

The graphic in Figure 5-9, made in 1912 when the Titanic
crashed into an iceberg in the Atlantic Ocean, also places
information within a familiar geographic context.

Each layer from top to bottom represents the time it would
take to travel across the ocean via a 17th century ship
(40 days), the Titanic (4 days), and by a not yet realized airplane (1 day). If only
you could fly the Atlantic! Grid lines separate the modes of transportation as
well as provide estimated travel times. Grids can also improve readability in
more traditional charts because they dictate spacing and reflect scale.

Introduce color as a visual cue, and there are additional considerations. For exam-
ple, you saw how those who are color-deficient see shades of red and green. If
you use red and green hues with the same saturation, the colors look the same
to those who are color-deficient. Color options also change based on what scale
you use for a chart or what you want to show. As shown in Figure 5-10, there
are three main categories of color scales, with variation within each.

FIGURE 5-8 Bar chart versus
bubble chart to show large counts