BBANDS

Overview of the Bollinger Bands Indictor.

Bollinger bands are a chart overlay, volatility indicator that show the upper and lower range of normal price movement based on standard deviation.

The centerline of Bollinger bands is typically a 20-day simple moving average. The upper and lower bands are twice the 20-day standard deviation of price above and below the centerline.

Source code for the Bollinger Bands (BBANDS) function is available here.