# BBands

0th

Percentile

##### 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

See EMA, SMA, etc. for moving average options; and note Warning section.
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"] ) # }