Bollinger Bands®

Created by John Bollinger, Bollinger Bands price channels depict volatility as standard deviation boundary line range from a moving average of price. Bollinger Bands® is a registered trademark of John A. Bollinger. [Discuss] 💬

// C# usage syntax
IReadOnlyList<BollingerBandsResult> results =
  bars.ToBollingerBands(lookbackPeriods, standardDeviations);

Parameters

param	type	description
lookbackPeriods	int	Number of periods (N) for the center line moving average. Must be greater than 1 to calculate; however we suggest a larger period for statistically appropriate sample size. Default is 20.
standardDeviations	double	Width of bands. Standard deviations (D) from the moving average. Must be greater than 0. Default is 2.

Historical price bars requirements

You must have at least N periods of bars to cover the warmup periods.

bars is a collection of generic TBar historical price bars. It should have a consistent frequency (day, hour, minute, etc). See the Guide for more information.

Response

IReadOnlyList<BollingerBandsResult>

• This method returns a time series of all available indicator values for the bars provided.
• It always returns the same number of elements as there are in the historical price bars.
• It does not return a single incremental indicator value.
• The first N-1 periods will have null values since there's not enough data to calculate.

BollingerBandsResult

property	type	description
Timestamp	DateTime	Date from evaluated TBar
Sma	double	Simple moving average (SMA) of price (center line)
UpperBand	double	Upper line is D standard deviations above the SMA
LowerBand	double	Lower line is D standard deviations below the SMA
PercentB	double	%B is the location within the bands. (Price-LowerBand)/(UpperBand-LowerBand)
ZScore	double	Z-score of current price (number of standard deviations from mean)
Width	double	Width as percent of SMA price. (UpperBand-LowerBand)/Sma

Utilities

• .Condense()
• .Find(lookupDate)
• .RemoveWarmupPeriods()
• .RemoveWarmupPeriods(removePeriods)

See Utilities and helpers for more information.

Chaining

This indicator may be generated from any chain-enabled indicator or method.

// example
var results = bars
    .Use(CandlePart.HL2)
    .ToBollingerBands(..);

Results can be further processed on PercentB with additional chain-enabled indicators.

// example
var results = bars
    .ToBollingerBands(..)
    .ToRsi(..);

See Chaining indicators for more.

Streaming

Use the buffer-style List<T> when you need incremental calculations without a hub:

BollingerBandsList bbList = new(lookbackPeriods, standardDeviations);

foreach (IBar bar in bars)  // simulating stream
{
  bbList.Add(bar);
}

// based on `ICollection<BollingerBandsResult>`
IReadOnlyList<BollingerBandsResult> results = bbList;

Subscribe to a BarHub for advanced streaming scenarios:

BarHub barHub = new();
BollingerBandsHub observer = barHub.ToBollingerBandsHub(lookbackPeriods, standardDeviations);

foreach (IBar bar in bars)  // simulating stream
{
  barHub.Add(bar);
}

IReadOnlyList<BollingerBandsResult> results = observer.Results;

See Buffer lists and Stream hubs for full usage guides.