Representing Data - Data Points: Visualization That Means Something - page 125

In contrast, the second chart shows the same data ordered instead by the
highest percentage of attainment in 2009. It starts with Wyoming and goes
down to Texas. This focuses on the more recent estimates, whereas still mak-
ing it easy to pick out the values for 2000 because generally speaking, states
with higher percentages in 2009 were higher in the rankings in 2000, too. That
said, you can also sort by the 2000 estimates and move the labels to the left
to shift focus in this direction.

Finally, the chart on the far right introduces color as a visual cue. This is the
same as the second chart that sorts by 2009 estimates, but color is used to
highlight states that increase the most by percentage. The District of Columbia,
which albeit isn't a state, had the greatest percentage increase, so it is shown
in black. The lower the increase, the lighter the states are shown. States in
between are shown with varying shades of green. So if you look at the indi-
vidual components of this chart, you get length, position, direction, and color
used as visual cues; it uses a Cartesian coordinate system; and a linear numeric
scale is used on the horizontal, with a categorical scale on the vertical.

You don't have to stop here. As shown in Figure 3-29, position and direction
can be used differently to show the increases from 2000 to 2009. Unlike the
previous charts, states are plotted on a linear scale that represents high school
attainment instead of on a categorical scale. Values are categorized by year on
the horizontal. This is essentially a couple of ticks on a time series plot. If you
were to show years in between, there would be more than two categories on
the horizontal axis. In any case, like in a time series plot, a greater slope from
point to point means a greater rate of change.

The chart on the right uses the same geometry as the one on the left, and
uses color to represent regions in the United States. So although you see
improvement with all states, you also see a lot of the states in the South
toward the bottom of the scale and Midwest and West states more toward
the top. Although, as is usually the case with real data, there are exceptions,
such as California in the West that is toward the bottom and Maryland that is
in the South is higher up.

Generally speaking though, the higher the attainment in 2000, the higher the
attainment was in 2009. This is obvious in Figure 3-30, which uses position as
a visual cue and linear scales on both axes.

FIGURE 3-28 (following page)
Change in high school educational
attainment between 2000 and 2009