BollingerEMA.efs

BollingerEMA.efs  

File Name: BollingerEMA.efs

Description:
Bollinger study with an exponential moving average basis line and bands at plus and minus 2 standard deviations.

Formula Parameters:

• nLength: Default is 20
• nStdDev: Default is 2

Notes:
NA

Download File:
BollingerEMA.efs


EFS Code:

/*****************************************************************
Provided By : eSignal. (c) Copyright 2003
*****************************************************************/

function preMain() {
	setPriceStudy(true);
	setStudyTitle("Bollinger Bands (EMA of Basis Line)");
	setCursorLabelName("Upper Band", 0);
	setCursorLabelName("EMA Basis", 1);
	setCursorLabelName("Lower Band", 2);
	setDefaultBarFgColor(Color.blue, 0);    // upper band
	setDefaultBarFgColor(Color.red, 1);     // basis line
	setDefaultBarFgColor(Color.blue, 2);    // lower band
}

var vEMA = null;
var vEMA1 = null;

var dPercent = 0.0;
var bPrimed = false;

function EMA(nLength, nClose) {
	var nBarState = getBarState();
	var dSum = 0.0;
	var dRef;

	if(nBarState == BARSTATE_ALLBARS || bPrimed == false) {
		dPercent = (2.0 / (nLength + 1.0));
		bPrimed = false;
	}

    if (nBarState == BARSTATE_NEWBAR) {
        vEMA1 = vEMA;
    }

	if(bPrimed == false) {
	    for(i = 0; i < nLength; i++) {
		    dSum += nClose[i];
	    }
		bPrimed = true;
		return (dSum / nLength);
	} else {
		return (((close() - vEMA1) * dPercent) + vEMA1);
	}
}

function main(nLength, nStdDev) {
	if(nLength == null || nLength <= 0) nLength = 20;
	if(nStdDev == null) nStdDev = 2;

	var vClose = getValue("Close", 0, -nLength);
	if(vClose == null) return;
    
    var sumX = 0;
    var sumX2 = 0;
    for (i = 0; i < nLength; ++i) {
        sumX += vClose[i];
        sumX2 += (vClose[i] * vClose[i])
    }
    var meanX = (sumX/nLength);
    var StdDev = Math.sqrt((sumX2/nLength) - (meanX*meanX));

    vEMA = EMA(nLength, vClose);
    
	var vUpper = vEMA + (nStdDev * StdDev);
	var vBasis = vEMA;
	var vLower = vEMA - (nStdDev * StdDev);

	return new Array(vUpper, vBasis, vLower);
}