A plot of a function that takes an angle θ as input and returns a distance r as output. It is plotted on a polar grid-graph paper with lines radiating out from the origin at fixed-angle intervals, and tick marks along those lines against which r can be plotted. For example, a plot of $r=x+y\theta$ will result in the Archimedes spiral. Polar plots are often used to show how antenna sensitivity and power output vary with direction.