Envelope

Envelope

upperEnv( length, bExponential, percentage [, source | sym() | inv()] [, barIndex] )

middleEnv( length, bExponential, percentage [, source | sym() | inv()] [, barIndex])

lowerEnv( length, bExponential, percentage [, source | sym() | inv()] [, barIndex] )

An envelope is composed of two moving averages. One moving average is shifted upward and the second moving average is shifted downward. Envelopes define the upper and lower boundaries of a security's normal trading range. A sell signal is generated when the security reaches the upper band, whereas a buy signal is generated at the lower band. The optimum percentage shift depends on the volatility of the security—the more volatile, the larger the percentage.

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 = upperEnv( 20, false, 10 );

               myStudy2 = middleEnv( 20, false, 10 );

               myStudy3 = lowerEnv( 20, false, 10 );

               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 = middleEnv( 20, false, 10 );

       //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 = middleEnv( 20, false, 10, 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 = upperEnv( 20, false, 10, 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 = lowerEnv( 10, true, 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 = middleEnv( 12, false, 4, sym( "MSFT,30" ) );

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

       myStudy = upperEnv( 10, false, 3, 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 = lowerEnv( 20, true, 7, close( inv(15) ) );

offsetSeries()