Visualizing Patterns over Time - Data Points: Visualization That Means Something - page 124

CrEATE A STEP ChArT
Illustrator doesn't have a tool to easily create step charts. R does, how-
ever, so you can create a base chart in R and then edit in Illustrator. Are
you starting to see a pattern here?
Figure 4-42 shows the final chart. It shows the change in postage rate for
letters via the United States Postal Service. Notice the changes don't hap-
pen on a scheduled basis. From 1995 to 1999, postage stuck at 32 cents.
That's 4 years without a change. However, more recently, there has been a
change once a year from 2006 to 2009.
FIGurE 4-42 Step chart showing change in postage rate