# 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]

```
// usage
IEnumerable<BollingerBandsResult> results =
quotes.GetBollingerBands(lookbackPeriods, standardDeviations);
```

## Parameters

`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 quotes requirements

You must have at least `N`

periods of `quotes`

to cover the warmup periods.

`quotes`

is a collection of generic `TQuote`

historical price quotes. It should have a consistent frequency (day, hour, minute, etc). See the Guide for more information.

## Response

```
IEnumerable<BollingerBandsResult>
```

- This method returns a time series of all available indicator values for the
`quotes`

provided. - It always returns the same number of elements as there are in the historical quotes.
- 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

`Date`

* DateTime* - Date from evaluated

`TQuote`

`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

See Utilities and helpers for more information.

## Chaining

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

```
// example
var results = quotes
.Use(CandlePart.HL2)
.GetBollingerBands(..);
```

Results can be further processed on `PercentB`

with additional chain-enabled indicators.

```
// example
var results = quotes
.GetBollingerBands(..)
.GetRsi(..);
```