Exploring Data Visually - Data Points: Visualization That Means Something - page 183

FIGURE 4-42 Heat map to show multiple variables
Parallel coordinates plots also arrange variables horizontally, but instead of
using color like a heat map, you use vertical position, as shown in Figure 4-44.
Each vertical axis represents a variable that typically ranges from the minimum
and maximum of that variable, so the highest value is plotted at the top and
the lowest at the bottom. Then lines are drawn left to right, positioned by the
variables of each observation.