Elder Ray is based on oscillators, labeling the components as "bull power" or "bear power." These are combined with an exponential moving average (EMA), which is a trend-following indicator essential to the calculation. Bull power is a simple calculation, derived by subtracting an exponential moving average (perhaps a 13-day EMA) of closing prices from a high price of any given security. Bear power subtracts the EMA from the corresponding low price of that trading day. Both bull power and bear power are plotted as histograms under the bar chart of your chosen security
Remember that price is a consensus of value for any given security at a particular point in time. The moving average is simply a consensus of value that is extended for a certain window of time. The 13-day EMA referenced earlier is the average consensus of value over the last 13 days.