Data visualization is critical to understanding the content of the data. Data analysts use visualization to examine, scrutinize, and validate their analysis before they report their findings. People making decisions use visualization to explore and question the findings before they develop action plans. Each group needs different graphics and visualization tools to do its work.

Data sets often come from a file and are typically displayed as a table or spreadsheet of rows and columns. If the data set is small and all the data can be displayed on a single page, it can be analyzed or the results presented as a table. But as the number of rows (observations) and columns (variables) increase, long lists of numbers and statistical summarizations of them do not tell us all we need to know. Data graphics help us understand the context and the detail together. They help us think visually and provide a powerful way to reason about large data sets.

While data graphics are centuries old, the graphical user interfaces available today on every computer enable interactive visualization tools to be included in information software products. For example, online newspapers contain interactive graphics that allow the reader to interactively explore data, such as the demographics of voters in elections, or the candidates' source of income. Visualization tools for data sets with many variables, in particular, must display relationships of three or more variables ...

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