Databases Reference
In-Depth Information
Figure 2.32
Temporal Component Slider
In response to the parameter requests, select “State” as the boundary, and
“State” again as the name of the attribute containing state name. Check
“Year” as the only temporal attribute.
Select “OK”.
After the map loads, zoom to the 48 contiguous states.
You should immediately detect that New York is the largest state (population
wise) and Pennsylvania is next. You might question the data if you thought that
California had the most people. The answer is found in the new slider in the
options panel. The slider is all the way to the left and the label above says: Year
1900. You are looking at the populations in 1900 (Figure 2.32).
To see the populations in subsequent years, slowly drag the slider to the
right. As you drag, you see the California color increasing to the more
saturated blue color and starting in the 1960s you see New York losing its
saturated blue color. This does not indicate that New York is losing
population. It indicates that New York's population is dropping relative
to the state with the most people. Thus, up until the 1960s, New York is the
most populous state and gets the fully saturated blue encoding. Once
California passes New York, California gets the fully saturated blue and
New York's color encoding becomes relative to California.
Move the slider back to 1900.
Check the radio button “Relative to Full Time Period”.
All of the states lighten considerably. This is because the encoding is relative
to the maximum over the full 110-year range. The maximum occurred in
California in 2009. As with the other color encoding options, you are cautioned
to always be aware of the currently selected option. Depending on the dataset,
you may want to see the encoding relative to the “full time period” and with a
different dataset relative to the currently “selected time”.
To animate the progress of population growth over time,
Select the “Start” button.
“Pause” and restart the animation a time or two by repeatedly selecting the
button. Do this when you want to take a closer look as the animation
progresses.
