Visualizing Patterns over Time - Data Points: Visualization That Means Something - page 94

is important. Although the examples are for specific charts, you can apply
the same principles to all sorts of visualization. Remember it's all about
the big picture.
Bars
The bar graph is one of the most common chart types. Most likely you've
seen lots of them. You've probably made some. The bar graph can be used
for various data types, but now take a look at how it can be used for tem-
poral data.
Figure 4-3 shows a basic framework. The time axis (the horizontal one,
that is, x-axis) provides a place for points in time that are ordered chrono-
logically. In this case the points in time are months, from January to June
2011, but it could just as easily be by year, by day, or by some other time
unit. Bar width and bar spacing typically do not represent values.
FIGurE 4-3 Framework of bar graphs