BollingerEMA.efs

[eSignal_JasonK]

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:


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);
}