Radar Charts are often used to compare two or more items or groups on various features or characteristics. However, as the number of groups increases, the user has a harder time making comparisons between groups. As the number of groups increase, the number of spokes of the radar chart increases. Users in general have a harder time comparing radial distances.You're better off using a scatter plot for this. If however, you still want to create a radar chart, you may want to the fmsb package.