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 securitythe more volatile, the larger the percentage.
Syntax
upperEnv( nLength , bExponential , nPercentage [, Series | sym() | inv() ][, nBarIndex ] )
middleEnv( nLength , bExponential , nPercentage [, Series | sym() | inv() ][, nBarIndex ] )
lowerEnv( nLength , bExponential , nPercentage [, Series | sym() | inv() ][, nBarIndex ] )
Parameters
Parameter: Description: Default:
n/a bExponential Required. Boolean true or false to use exponential calculations.
n/a nPercentage Required. Number expressed as a percentage to determin envelope width (i.e. enter 10 for 10%).
n/a Series or
sym() or
inv() [Optional] Series Object or function of sym() or inv() to determine symbol/interval source for the study.
Chart's sym/inv nBarIndex [Optional] Bar index of series to retrieve.
n/a
Return Value(s)
Returns a Series Object when nBarIndex is not specified.Returns a single value when nBarIndex is specified.
Notes
Only available in versions 7.9 or later.
Code Examples
Single Line Indicator:
function main() { return new Array(upperEnv(20, false, 10), middleEnv(20, false, 10), lowerEnv(20, false, 10) );}
Single Line Study-on-Study Indicator:
function main() { return new Array(upperEnv(20, false, 10, hl2()), middleEnv(20, false, 10, hl2()), lowerEnv(20, false, 10, hl2()) );}
Retrieve single values:
function main() { var nValue_0 = middleEnv(20, false, 10, 0); // Current Bar Index var nValue_1 = middleEnv(20, false, 10, -1); // Prior Bar Index return new Array(nValue_0, nValue_1);}
Initialize Series Objects:
//global Series Object variablesvar xStudy1 = null;var xStudy2 = null;var xStudy3 = null;function main() { if (xStudy1 == null) xStudy1 = upperEnv(20, false, 10); if (xStudy2 == null) xStudy2 = middleEnv(20, false, 10); if (xStudy3 == null) xStudy3 = lowerEnv(20, false, 10); // retrieve single values for conditional statements var nValue1_0 = xStudy1.getValue(0); // Current Bar Index value var nValue2_0 = xStudy2.getValue(0); // Current Bar Index value var nValue3_0 = xStudy3.getValue(0); // Current Bar Index value var nValue1_1 = xStudy1.getValue(-1); // Prior Bar Index value // Plot Current Bar Index Value return new Array(nValue1_0, nValue2_0, nValue3_0); }
Initialize a Series Object based on an external interval:
// global Series Object variablesvar xStudy1 = null;var xStudy2 = null;var xStudy3 = null;var bInit = false; // Initialization flagfunction main() { if (bInit == false) { xStudy1 = upperEnv(20, false, 10, inv(20)); // 20-min interval xStudy2 = middleEnv(20, false, 10, inv(20)); // 20-min interval xStudy3 = lowerEnv(20, false, 10, inv(20)); // 20-min interval bInit = true; } // retrieve single values for conditional statements var nValue1_0 = xStudy1.getValue(0); // Current Bar Index value var nValue1_1 = xStudy1.getValue(-1); // Prior Bar Index value // Synchronized Series plot return new Array(getSeries(xStudy1), getSeries(xStudy2), getSeries(xStudy3) ); }
Initialize a Series Object based on an external symbol and interval:
// global Series Object variablesvar xStudy1 = null;var xStudy2 = null;var xStudy3 = null;var bInit = false; // Initialization flagfunction main() { if (bInit == false) { xStudy1 = upperEnv(20, false, 10, sym("IBM,20")); // IBM 20-min interval xStudy2 = middleEnv(20, false, 10, sym("IBM,20")); //IBM20-min interval xStudy3 = lowerEnv(20, false, 10, sym("IBM,20")); //IBM20-min interval bInit = true; } // retrieve single values for conditional statements var nValue1_0 = xStudy1.getValue(0); // Current Bar Index value var nValue1_1 = xStudy1.getValue(-1); // Prior Bar Index value // Synchronized Series plot return new Array(getSeries(xStudy1), getSeries(xStudy2), getSeries(xStudy3) ); }
See Also
Series Object
getSeries()
Built-in Study Functions
eSignal Forum Search Engine
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