Database Reference
In-Depth Information
(a) A thousand words
(b) Apicture
Fig. 1. “A picture is worth a thousand words”
example shown in Figure 1. Part (a) shows a spreadsheet with data for the 50
states and the District of Columbia in the U.S. Also shown are the percentage
of citizens of each state with a college degree and the per capita income of the
states' citizens.
Given just the spreadsheet, answering a question such as, “Which state has
the highest average income?” is not too dicult. A simple scan of the income
column likely will produce the correct answer in a few seconds. More complex
questions can be quite challenging given just the data, however. For example,
are the college degree percentage and income correlated? If they are correlated,
are there particular states that are outliers to the correlation? These questions
are much more dicult to answer using only the spreadsheet.
Now, let us turn to a graphical visualization of the data. If we simply draw
the data in a scatterplot as shown in part (b), the questions now become much
easier to answer. Specifically, there does appear to be an overall correlation
between the two attributes and states such as Nevada and Utah are outliers on
the correlation. The simple act of plotting the spreadsheet data in this more
meaningfully communicative form makes these kinds of analytic queries easier
to answer correctly and more rapidly.
Note that the spreadsheet itself is a visual representation of the data that
facilitates queries as well. Consider how dicult the three questions would be if
the data for each state was recorded on a separate piece of paper or webpage.
Or worse yet, what if the data values were read to you and you had to answer
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