Radar Charts are very useful when you need to compare several items by a number of parameters and features,
which can be measured quantitatively or in percent. It uses two-dimensional coordinate system, but while
y-axis looks familiar, x-axis looks like a polygon, which vertexes are categories (or parameters by which we
compare the entities). These charts are quite popular in many different areas, such as online-games or
Stacked Area Charts are used when we want to show that those values that we display and compare all together
form a whole, and using Percent Stacked Area series is reasonable when we need to compare the percentage
values those series bring to a whole. The y-axis is ranged from 0 to 100 percent; since in Radar Charts
x-axis takes a form of a polygon with a number of vertexes equal to the number of categories; all series
together fill all area inside this polygonal x-axis.
This Chart displays the sales volumes for four regions in a period from 2007 to 2011. Each series represents
a region, all colored differently. You can switch series on and off using legend; when you turn any series
off or on, the percentage values for all series that remain will be recalculated. When you hover a series on
a plot, the nearest point becomes highlighted, and you will select this point if you click on a series at
this moment. You can select a number of points by holding the Shift of Ctrl key.