Graphics Reference
In-Depth Information
This is practically a direct translation of the last three columns in the table.
Each row represents the values for a state, and each column is a level of attain-
ment. Each bar chart has its own linear scale, but the increments are spaced
equally and start at zero percent. States are sorted by estimated percent of
people with a high school diploma or equivalent, in descending order, rather
than alphabetically, like in the table. Instead of giving the national average
its own row, it's presented as a vertical dotted line to provide a sense of low
and high. Color hue—gray, light blue, and blue—is used to indicate three
separate estimates.
Break it down. That's length (bars), color (each bar chart), and position (lines for
national averages) as visual cues, a Cartesian coordinate system, linear scales
for each of the bar charts, and a categorical scale for the sorted states. The
title and subtitles provide context for what the data is about.
If you are more interested in the changes between 2000 and 2009 than you
are just the 2009 percentages, Figure 3-28 shows a few options that shift focus.
Length and position are still used, as well as a linear scale on the horizontal
axis and a categorical scale on the vertical. However, the context and layout
are different than the bar charts. Some other visual cues are also incorporated.
An open circle represents the high school attainment in 2000 for each state, and
the solid circles represent the same for 2009. The dots are placed in the same
position vertically, and a line is used to connect the two dots. The longer the
line is, the greater the change, by percentage points, was from 2000 to 2009.
The shift from open circle to closed circle provides a sense of direction. In this
example, high school attainment in all states improved, so your eyes always
shift from left to right, but if attainment decreased in one of the states, you
could use the same visual cue. For example, if there were a decrease from 80
percent to 70 percent, the solid dot would be on the left of the open one. You
can also use arrows if you want to highlight direction more prominently. All
states showed increases in this example, though, so a focus on the magnitude
of the changes and the values of the endpoints was more appropriate.
You can see how a change in sorting can shift focus. States are sorted alphabet-
ically in the first chart, and the lack of visual order makes it more challenging
to make comparisons. You can see the increases and it's easy to find a state
of interest, but as an overall picture, you don't get much.
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