# BBands

##### Bollinger Bands

Bollinger Bands are a way to compare a security's volatility and price levels over a period of time. Developed by John Bollinger.

- Keywords
- ts

##### Usage

`BBands(HLC, n = 20, maType, sd = 2, ...)`

##### Arguments

- HLC
Object that is coercible to xts or matrix and contains High-Low-Close prices. If only a univariate series is given, it will be used. See details.

- n
Number of periods for moving average.

- maType
A function or a string naming the function to be called.

- sd
The number of standard deviations to use.

- …
Other arguments to be passed to the

`maType`

function.

##### Details

Bollinger Bands consist of three lines:

The middle band is generally a 20-period SMA of the typical price ([high +
low + close]/3). The upper and lower bands are `sd`

standard deviations
(generally 2) above and below the MA.

The middle band is usually calculated using the typical price, but if a univariate series (e.g. Close, Weighted Close, Median Price, etc.) is provided, it will be used instead.

##### Value

A object of the same class as `HLC`

or a matrix (if
`try.xts`

fails) containing the columns:

- dn
The lower Bollinger Band.

- mavg
The middle Moving Average (see notes).

- up
The upper Bollinger Band.

- pctB
The %B calculation.

##### Note

Using any moving average other than SMA will result in inconsistencies between the moving average calculation and the standard deviation calculation. Since, by definition, a rolling standard deviation uses a simple moving average.

##### References

The following site(s) were used to code/document this indicator: http://www.fmlabs.com/reference/Bollinger.htm http://www.fmlabs.com/reference/BollingerWidth.htm http://www.equis.com/Customer/Resources/TAAZ/?c=3&p=36 http://www.linnsoft.com/tour/techind/bb.htm http://stockcharts.com/education/IndicatorAnalysis/indic_Bbands.html http://stockcharts.com/education/IndicatorAnalysis/indic_BBWidth.htm

##### See Also

See `EMA`

, `SMA`

, etc. for moving average
options; and note Warning section.

##### Examples

`library(TTR)`

```
# NOT RUN {
## The examples below show the differences between using a
## High-Low-Close series, and just a close series when
## calculating Bollinger Bands.
data(ttrc)
bbands.HLC <- BBands( ttrc[,c("High","Low","Close")] )
bbands.close <- BBands( ttrc[,"Close"] )
# }
```

*Documentation reproduced from package TTR, version 0.23-1, License: GPL-2*