Chart Design: A Few Tips and Hints

The charting area is the focal point of the chart. The graphical, dramatic representation of numbers as bars, risers, lines, pies, and the like is what makes a chart so powerful. So make your charting area as prominent as possible without squeezing other chart elements off the page. If you can still get your point across without footnotes, axis titles, or legends, do so to make the charting area bigger. However, remember that the document needs to communicate enough information to be a stand-alone document. The following is a list of tips to keep in mind when designing your chart.

Less is more: Do not try to put too many series in a chart. Line charts are especially intolerant of overcrowding. More than three or four lines, particularly if the lines follow much the same direction, is visually confusing. The only exception to this rule is creating a line chart of several series that people would not expect to be similar.

Group bars to show relationships: Group bars together tightly if you are trying to suggest that they belong together. If you are showing a group of bars over a series of years, for example, it makes sense to cluster the bars for each year and leave a little extra space between years. If there is no need to do this with your chart data, put more space between your bars and make them a little wider so they are easier to see.

Add definition with black outlines: Give the bars in bar charts, the slices in pie charts, and the risers in 3-D charts a little definition by making their outlines black, or a dark, brilliant color. If you are making your chart into a slide, the people at the back of the room will appreciate being able to distinguish the elements.

Use grids in moderation: When using grid lines in your charting area, use only as many as are needed to get an approximate idea of the value of any given data point in the chart. Too many grid lines create visual clutter. Balance horizontal and vertical grid lines so that the rectangles they create are not too long and narrow or tall and narrow. Use soft colors, such as gray, for grid lines. Once you have defined the color and weight of the grid lines, make sure the chart frame (the frame around the charting area) is black or a dark, brilliant color and heavier than the grid lines.

Choose colors carefully: When choosing colors, use your company's corporate colors where possible and appropriate. Failing that, you can use software-supplied templates or color wheels. Also consider where your chart will appear. If it is going to be part of a computer screen show or a slide presentation in a large room, use strong, coordinating colors that attract attention and help the people at the back of the room distinguish the individual series. However, if it is going in a publication where it will be examined at close range, keep the colors softer so you do not overwhelm the reader.

Limit use of typefaces: Use one typeface, or at most two, on each chart, and use the same size and weight for similar elements such as the axes and legend text. A recommended setting for these is in 12 to 18 points and bold. If you use the bold and italic fonts in a typeface, as well as different sizes, you can generate enough typographic variety without going outside that type family.

Choose legible typefaces: Pick a typeface that looks clear in smaller sizes and in bold, especially if your chart is to be printed in a small size in a publication, or if it will be viewed by a large audience in a big room. If your title is big enough, you can use just about any typeface for it, and it will be legible. However, for legend text, axes, footnotes and the like, take more care. Use faces that are neither too light nor too heavy.

Set type against an appropriate background: Be careful about the background behind your type. Some color combinations, such as pink or violet type and a medium or dark blue background, could make your audience feel a little dizzy. If you are using a dark background color, your type must be bright enough to be readable; it should not look as if the background is trying to "swallow it up." If you are using light type on a dark background, use a bold weight, especially with smaller type sizes. Complex fill patterns in the background can also make type hard to read, particularly smaller items like legend text and axis scales.

Use pattern fills with moderation: Many charting software packages can create just about any kind of color combination or fill pattern you can imagine. But do not become carried away with color and patterns without thinking about your output device. Sophisticated fill patterns take up more disk space and take longer to print on color printers.