Bollinger Bands

Bollinger Bands

upperBB( length, stdDev [, source | sym() | inv()] [, barIndex] )

middleBB( length, stdDev [, source | sym() | inv()] [, barIndex] )

lowerBB( length, stdDev [, source | sym() | inv()] [, barIndex] )

Bollinger Bands (created by John Bollinger) are similar to moving average envelopes. The difference between Bollinger Bands and envelopes is that envelopes are plotted at a fixed percentage above and below a moving average, whereas Bollinger Bands are plotted at standard deviation levels above and below a moving average. Since standard deviation is a measure of volatility, the bands are self-adjusting, widening during volatile markets and contracting during calmer periods.

Parameters

To Create a Series

var myStudy1 = null;

var myStudy2 = null;

var myStudy3 = null;

var bInit = false;

function main() {

var myVar1;

var myVar2;

var myVar3;

       if ( bInit == false ) {

               myStudy1 = upperBB( 20, 2 );

               myStudy2 = middleBB( 20, 2 );

               myStudy3 = lowerBB( 20, 2 );

               bInit = true;

       }

       //retrieve the current values

       myVar1 = myStudy1.getValue(0);

       myVar2 = myStudy2.getValue(0);

       myVar3 = myStudy3.getValue(0);

       return new Array( myVar1, myVar2, myVar3 );

}

To Retrieve a Single Value

function main() {

       ...

       ...

       myVar = middleBB( 10, 1.5 );

       //do something with the value in myVar

}

Calling Examples

       //create a study that uses IBM as the symbol along with whatever bar

       //interval you are using in the chart where the script is loaded

       myStudy = middleBB( 20, 2, sym( "IBM") );

       //create a study that uses the 15-min bar interval, regardless of the bar 

       //interval of the chart in which the script is loaded

       myStudy = upperBB( 20, 2, inv(15) );

       //create a study that uses the Daily bar interval, regardless of the bar 

       //interval of the chart in which the script is loaded

       myStudy = lowerBB( 10, 1.5, inv("D") );

       //create a study that will be based on MSFT 30-min bars, regardless of

       //the symbol/bar interval of the chart in which the script is loaded

       myStudy = middleBB( 20, 1, sym( "MSFT,30" ) );

       //create a study that will be based on the high.

       myStudy = middleBB( 10, 2, high() );

       //create a study that will be based on the close, using 15-min bars, regardless of 

       //the bar interval of the chart in which the script is loaded

       myStudy = upperBB( 12, 2, close( inv(15) ) );

offsetSeries()