2017 Feb: Exponential Standard Deviation Bands by Vitali Apirine

2017 Feb: Exponential Standard Deviation Bandsby Vitali Apirine

File Name: ESDB.efs 

Description: 
Exponential Standard Deviation Bands by Vitali Apirine

Formula Parameters: 

ESDB.efs

• Length: 20
• # of EStdDev: 2

Notes: 
The related article is copyrighted material. If you are not a subscriber of Stocks & Commodities, please visit www.traders.com.

/*********************************
Provided By:  
eSignal (Copyright c eSignal), a division of Interactive Data 
Corporation. 2016. All rights reserved. This sample eSignal 
Formula Script (EFS) is for educational purposes only and may be 
modified and saved under a new file name.  eSignal is not responsible
for the functionality once modified.  eSignal reserves the right 
to modify and overwrite this EFS file with each new release.

Description:        
    Exponential Standard Deviation Bands by Vitali Apirine

Version:            1.00  12/07/2016

Formula Parameters:                     Default:
Length                                  20
# of EStdDev                            2



Notes:
The related article is copyrighted material. If you are not a subscriber
of Stocks & Commodities, please visit www.traders.com.

**********************************/


var fpArray = new Array();

function preMain(){
    setPriceStudy(true);
    setCursorLabelName("Upper", 0);
    setCursorLabelName("Middle", 1);
    setCursorLabelName("Lower", 2);
    setDefaultBarFgColor(Color.RGB(255,106,0),1);
    
    var x = 0;
    fpArray[x] = new FunctionParameter("Length", FunctionParameter.INTEGER)
    with(fpArray[x++]){
    setLowerLimit(1);
    setDefault(20);
    setName("Length");
    }
    fpArray[x] = new FunctionParameter("MFactor", FunctionParameter.NUMBER)
    with(fpArray[x++]){
    setLowerLimit(1);
    setDefault(2);
    setName("# of EStdDev");
    }
}

var bInit = false;
var bVersion = null;

var xClose = null;
var xEMA = null;
var xStdDev = null;
var xUpBand = null;
var xLwBand = null;
var bUpFlag = false;
var bLwFlag = true;

function main(Length, MFactor){
    if (bVersion == null) bVersion = verify();
    if (bVersion == false) return;
    
    if (getBarState() == BARSTATE_ALLBARS)
        bInit = false;
    
    if (!bInit){
        xClose = close();
        xEMA = ema(Length, xClose);
        xStdDev = efsInternal("ExpStdDev", xClose, xEMA, Length);
        xUpBand = efsInternal("UpperLower", xEMA, xStdDev, MFactor, bUpFlag);
        xLwBand = efsInternal("UpperLower", xEMA, xStdDev, MFactor, bLwFlag);
        bInit = true;
    }

    nUpBand = xUpBand.getValue(0);
    nMidBand = xEMA.getValue(0);
    nLwBand = xLwBand.getValue(0);

    if ((!isNull(nUpBand)) && (!isNull(nMidBand)) && (!isNull(nLwBand)))
        return [nUpBand, nMidBand, nLwBand];
}

function ExpStdDev(xClose, xEMA, len){
    var nSum = 0;
    var nEMA = xEMA.getValue(0);
    for (var i = 0; i < len; i++){
        var nClose = xClose.getValue(-i);
        if (!isNull(nClose) && !isNull(nEMA)){
            nSum += Math.pow((nClose - nEMA), 2);
        }
    }
    return (Math.sqrt(nSum/len));
}

function UpperLower(xEMA, xStdDev, MFactor, bFlag){
    var nEMA = xEMA.getValue(0);
    var nStdDev = xStdDev.getValue(0);
    nStdDev *= MFactor;
    
    if (bFlag == bLwFlag)
        nStdDev = -nStdDev;
    return (nEMA + nStdDev);
}

function verify(){
    var b = false;
    if (getBuildNumber() < 779){
        
        drawTextAbsolute(5, 35, "This study requires version 10.6 or later.", 
            Color.white, Color.blue, Text.RELATIVETOBOTTOM|Text.RELATIVETOLEFT|Text.BOLD|Text.LEFT,
            null, 13, "error");
        drawTextAbsolute(5, 20, "Click HERE to upgrade.@URL=http://www.esignal.com/download/default.asp", 
            Color.white, Color.blue, Text.RELATIVETOBOTTOM|Text.RELATIVETOLEFT|Text.BOLD|Text.LEFT,
            null, 13, "upgrade");
        return b;
    } 
    else
        b = true;
    
    return b;
}