Whether they be pie charts or digital stills, figures are fundamentally defined as drawn or photographed pictures. Basics about how they are used follow:

• Be sure to name figures properly; do not accidentally call them tables, even if they include words and numbers.
• As a general rule, orient figures from left to right, in that readers are used to following that path with their eyes.
• Use line graphs to plot continuous variables, such as time or temperature. Line graphs are especially handy to show relationships among measured variables.
• Use pie charts or bar graphs to depict discontinuous variables, such as percentages or sampling that occurred in intervals. Pie charts are especially useful when you wish to show the relation of parts to a whole.
• Use photographs or drawings for material that is large in scale, such as a cloud or an office building, or very small in scale, such as the grain boundaries of a sample.
• Use flowcharts to represent pathways of activities and outcomes. Most flowcharts use simple geometric shapes (circles, rectangles) to represent activities and arrows to indicate change from one event to the next.
• If possible, label the axes of graphs with full words: “Temperature versus time” rather than “T versus t.”
• Be certain that your legend—that part of the figure where you define any symbols or other visual markers that appear—is readable, clear, and meaningfully placed. As long as it does not overwhelm the rest of the figure, do not be afraid to make the legend large to enhance its readability.
• Use footnotes (a simple asterisk to indicate them will do) for explanatory material such as the number of respondents to a survey or the fact that certain values were estimated.