Chart of the Month – December 2011 – Radar Charts with Target Backing
Radar charts aren't used as often as they should be. They're a very useful tool. Presenters seem to be very comfortable with showing volumes and comparisons as column or line charts, which also work but aren't nearly as concise. The reason radar charts aren't used more broadly may be because they can be difficult to decipher, especially when there are lots of lines and categories. In those cases, it's probably better to go with a more linear approach to displaying data. But if you have only a few lines and a few categories, consider placing a target-type graphic behind the radar chart to help your audience make value comparisons more easily. The radar charts cannot be formatted to accept any type of fill for the value bands, so this is the "fix."
Size the circles so that they are the same size as the bands and then layer then so that are all are visible. Move them behind the radar chart. Don't worry that the radar chart's grid lines have hard corners and the target background is comprised of circles. They still work together very well. When choosing your target colors, you can use the lighter hues from your color palette. Or, if you wish, you can use shades of gray or other complementary color. Just be sure that there is a lot of contrast between the data lines and the colors in the target.
The two charts are identical except that one uses the target-type graphic. You can see that they values are much more apparent with the targets. Consider using this device the next time you have to compare values and categories.