Nancy J. Schmitt
In
The Visual Display of Quantitative Information
, Edward Tufte discusses many of the basic principles of creating good graphs. He credits William Playfair in the mid 1700 to early 1800s to have “ developed or improved upon nearly all fundamental graphical designs, seeking to replace conventional tables of numbers with the systematic visual representations of his ‘linear arithmetic’.” page 10. Many of the graphic techniques that Playfair invented and published are the underpinnings of good graph making today. It is important to note that the graphs that Playfair created were all business graphs. The graph’s purpose was to convey a specific idea in a manner clearer than by tablulating data and describing it in words. Graphs helped the reader to get to the gist of the information quicker and draw more informed conclusions.
The basic principles of creating good graphs include data integrity paired with graphical integrity. The size of objects in the graph should be proportional to the data they are depicting. There needs to be a consistency of the physical size of graphical elements relative to the data being represented. Optical illusions should not be used to draw the eye and the brain to make conclusions that are not consistent with what the original data shows. Graphs should not distort data through visual graphics and optical illusions.
Graphs should be designed with the idea of simplicity, using minimal non-duplication of data and data should be presented in context. All of the necessary components should be included, not just a portion that would deceive the reader. Careful setting of horizontal and vertical grid points so as not to distort the data shown is also important. Omitting grid lines or portions of them can eliminate unnecessary ink and clarify the graph.
From the day of Playfair until today, there have been many graphical displays of data, of which many have not adhered to good graph making techniques. In fact with the advent of the computer, many times graphs are hastily prepared and published without the proper editing.
Students today need to be able to create graphs both with paper and computers. Paying attention to the above guidelines will help create graphs that are useful and accurate.
