Graphics (tables, figures, and graphs) are not just salad dressing; they are not just illuminations scribed in the margins by hightech monks to increase the glory of science. Rather graphics are integral to a document's logic, structure, and purpose. Technical papers are often structured around the graphics.
Literally, a graphic makes the reader ``see'' the author's idea. By their nature, Graphic and textual representations differ. text is one dimensional and, well, composed of words. Text is two dimensional and presents its ideas visually.
I have 6 things to say about graphics:
- A picture is worth a thousand words; the higher the information density, the better. As a corralary, a picture that is worth fewer than a thousand words should be removed from a document.
- As with text, structure will be vital if large amounts of information are to be conveyed. Expository issues of purpose, context, beginning/middle/end, and design apply to graphics. Often the graphic's structure is predetermined and well known by both the reader and the author. When the structure is new, extra care must be taken to convey order the reader.
- Graphics must convey information visually; the reader must be able to ``see'' something when looking at the figure. While the expository issues are similar, the principles of graphic design can be very different, and the tools and methods used to achieve visual impact are often quite different from those used to produce textual impact. For an in depth coverage of graphic design principles relevant to technical writing, I can recommend Edward Tufte's ``The Visual Display of Quantitative Information'' and ``Envisioning Information.''
- The graphic must be referenced in the text. ``See Figure 1'' is not sufficient. Additionally, the reader must be told what to ``see'' when looking at the graphic, and how the figure relates to the text.
- The use of graphics provides a second representation of the ideas found in the text. Such multiple representation has two benefits. First, because readers preferentially absorb information from some media, a variety of representations -- pictures, graphs, tables, and text -- gives the reader a better chance of immediatly grasping the author's idea. Secondly, these multiple representations provide a more complete picture of a complicated idea. If the reader can approach the same idea from different vantages, the big picture is more easily grasped. The understanding of a complicated idea is complete when the reader can comfortably switch between different the idea's representations. (See the work of Judah Scwartz for more information on the relationship between multiple representations and learning complex ideas.)
- Like text, graphics are edited; they go through drafts, through write-read-think-edit-write cycles.
For more on graphics, I recommend Edward Tufte's The Visual Display of Quantitative Information and Envisioning Information.