Corona Plots were developed by Dr. John Elder to instantly visualize the effect of selecting stocks for an investment portfolio according to all possible linear weightings of two features of the stocks. A Corona Plot illustrates the return of the top-scoring stocks (say top 10%) when the score comes from the relative weighting of the features given by the angle along the circle. The baseline, or return of all the stocks, is represented by the black circle, so greater portfolio returns appear outside the circle, and lesser ones inside. For instance, the 45-degree point along the circle would represent the result of choosing a decile of stocks according to a score which is an average between the two features. Relative returns are also colored by a temperature-like scale where red is the best and blue the worst.