Relative strength is a ratio of a stock price performance to a market average (index) performance.
It is not to be confused with relative strength index.
To calculate the relative strength of a particular stock, divide the percentage change over some time period by the percentage change of a particular index over the same time period.
[2] Relative Rotation Graphs (RRG) show the relative strength and momentum of mood swings in the market compared to benchmarks.
The "JdK RS-Ratio" (relative strength, RS) was developed by Julius de Kempenaer, a sellside analyst in The Netherlands.