Conceiving and Reasoning Visualization Design Options - Data Visualization: A Successful Design Process - page 82

Well yes, of course we do, but the inclusion of terms such as "maximize" and "as
possible" allude to the specter of alternative influences. You see, for certain contexts,
as we outlined in the early chapters, you might be seeking to explore different
aesthetic forms of representation. And yes, sometimes this might involve certain
sacrifices in terms of the precision of interpretation.
To frame this section, we first need to learn about visual variables. A visual variable
is the specific form we assign to data in order to represent it visually. It could be the
length or height of a bar, the position of a point on an axis, the color of a county on a
map, or the connection between two nodes in a network.
Each of the chart types that we come to take as common representation methods
are based on the deployment of a single or, more commonly, combination of several
visual variables at once. Using multiple variables, in particular, enables a designer to
efficiently express extra layers of meaning behind the properties of a single mark, as
the next example demonstrates.
Image from "How Much Money do the Movies we Love Make?"
( http://vallandingham.me/vis/movie/ ), created by Jim Vallandingham
In this bubble chart visualization, each mark involves a combination of several visual
variables representing a range of different data variables:
• The position on the x axis represents a film's profit.
• The position on the y axis represents the average review percentage
rating of each film.