• Chart-based graphics

Chart-based graphics are graphics that present numerical information in a non-text form. These forms are likely to be proportional representations of the numbers themselves. These are what many people refer to when they talk about informational graphics.

Chart-based graphics have become highly popular in today’s newspapers. Computer software has made them relatively easy to produce (as we shall see later in this chapter). Many journalists today spend a great deal of time gathering the information that can be presented in charts.

In addition to the principles of accuracy and clarity, informational graphics should share a number of other characteristics. The following are some of those characteristics:

• Simplicity. Graphics can be complex, but their appearance should be uncluttered. One of the criticisms of many graphics is that they are “chartoons” — that is, they have too many little figures and drawings that do not add to the reader’s understanding of the information in the graphic. A graphic should contain the minimum items necessary for understanding the information and the maximum items for good appearance.

• Consistency. Publications often develop a graphics style just as they adopt a writing style. This style includes rules about what kind of type is used, when color is appropriate, how information is attributed, and a variety of other matters. Like style rules for writing, these rules help both the staff in producing graphics and the reader in understanding them.

• Attribution. Information in graphics should be attributed, just as information in news stories should be attributed. As with other information in a publication, sometimes the source is obvious and does not need to be specified. In other cases, attribution is vital to the understanding of a graphic.

• Headlines. Oddly enough, one of the most difficult things about producing an informational graphic is writing its headline. Headlines for graphics do not have to follow the rules of headlines for articles; in most publications, they can simply be labels. They need to identify the central idea of the graphic, however, and this is difficult to do in just a few words. One approach many graphic journalists use to writing a headline for a graphic is to write it before the graphic is built. Doing that gives them the central idea to keep in mind while producing the graphic.

Most mass media publications use three types of chart-based graphics: the bar chart, the line chart, and the pie chart. (There are other types of charts for presenting numerical information such as the scattergraph, but these are not commonly found in the mass media.) Each type of chart is best used for presenting certain types of information and is inappropriate for other types of information. Editors need to understand what charts are appropriate for what types of information.

Bar charts

The bar chart is the most popular type of chart because it is easy to set up, and it can be used in many ways. The bar chart uses thick lines or rectangles to present its information. These rectangles represent the amounts or values in the data presented in the chart. (There are technically two types of bar charts. One uses the name bar chart and refers to charts in which the bars run horizontally. The column chart refers to bar charts in which the bars run vertically. Column charts are more commonly used when time is an element in the data. For the purposes of this text, however, we will not make a distinction between the bar and column chart.)

The two major lines in a bar chart are the horizontal axis, known as the x-axis, and the vertical axis, known as the y-axis. Both should have clearly defined starting points so that the information in the chart is not distorted, particularly the axis that represents the amounts in the graph.

Line charts

Whereas the bar chart may show change over time, the line chart must show change over time. It can also show a change in relationships over time. In some instances, it is preferable to the bar chart because it is cleaner and easier to decipher.

The line chart uses a line or set of lines to represent amounts or values, and the x-axis represents time. One of the standard conventions of the line chart is that the x-axis represents the time element and the y-axis represents the amounts or quantities being represented.

Line charts can use more than one line to show not only how one item has changed but the relationship of changes of several items. Data points can be represented by different shapes for each item. The danger with multiple line charts is that too many lines can be confusing to the reader. Graphic journalists should avoid putting more than three lines in a line chart.

Pie charts

The pie chart is another popular means of showing data, but its use is specialized. A pie chart should show how an entity or item is divided up, and the divisions are most commonly expressed in percentages that add up to 100 percent. Figures also may be used to identify the parts of a pie chart, but it is important that the creator of a pie chart keep the concept of percentages in mind.

Despite the strict limits of the kind of data that can be shown in a pie chart, this type of chart can be used in a variety of ways. A pie chart can show only one set of data at a time, but several charts can be used together to help compare sets of data, as in the set of pie charts on this page that depict the racial breakdown of populations in three major cities.