Often the most effective way to describe, explore, and summarize a set of numbers–even a very large set–is to look at pictures of those numbers.
Graphics visually display data by using points, lines, a coordinate system, numbers, symbols, words, shading, and color. The aim of data visualization is to establish the main features of the data and to guide in choosing the appropriate statistical techniques. Furthermore, visualization procedures help in spotting errors and unusual values in the data allowing corrective steps to be taken early in the analysis.
Theorists like Edward Tufte have defined the requirements for the attainment of excellence in statistical graphics.