Visualizing Proportions - Data Points: Visualization That Means Something - page 148

after you get the hang of things. Now have another look at Protovis in the
next section.
Stack Them Up
In the previous chapter you used the stacked bar chart to show data over
time, but it's not just temporal data. As shown in Figure 5-11, you can also
use the stacked bar chart for categorical data.
FIGurE 5-11 Stacked bar chart with categories
For example, look at approval ratings for Barack Obama as estimated
from a Gallup and CBS poll taken in July and August 2010. Participants
were asked whether they approved or disapproved of how Obama has dealt
with 13 issues.