Visualizing with Clarity - Data Points: Visualization That Means Something - page 550

FIGURE 5-6 Connecting visual
cues to what data represents
You must instead maintain the connection between visual cues and data
because the data is what connects a graphic to the real world. So readability
is key. Allow comparisons, consider the context of your data and what it rep-
resents, and structure shapes and colors (and the space around them) for clarity.
ALLOW COMPARISONS
Allowing comparisons across points is the main purpose of visualizing data.
In table form, you can compare only point by point, so you place data in a
visual context to see how big one value is relative to the rest and how all the
individual data points relate to each other. As a way to better understand data,
your visualization isn't useful if it doesn't fill this basic requirement. Even if
you just want to show that values are equal across the board, the key is still
to allow that comparison and conclusion to be made.
Traditional graphs, such as the bar, line, and dot plots that you've seen through-
out this topic were designed to make comparisons as straightforward and
obvious as possible. They abstract the data into basic geometric shapes so
that you can compare length, direction, or position. However, as shown in
Figure 5-7, you can apply small variations to these charts that can make a
graphic more or less challenging to read.
You saw how area should be used as a visual cue in Chapter 3, “Representing Data.”
When area is used to indicate values, determine the size of shapes such as bubbles
and squares by their total area rather than the length of radius or side length.
Essentially, the size of shapes are based on how people interpret them visually.
However, also keep in mind that it can be harder to see small changes between
two-dimensional shapes than it is to see differences between position or length.
This is not to say to avoid area as a visual cue. Instead, area is more useful when
there are exponential differences between values. When small differences are
important, look to a different visual cue, such as position or length.