/*********************************************************
Alexis C. Montenegro © June 2005                          
Use and/or modify this code freely. If you redistribute it
please include this and/or any other comment blocks and a 
description of any changes you make.                      
**********************************************************/

var fpArray = new Array();

function preMain() {
    setPriceStudy(true);
    setStudyTitle("Keltner Channel");
    setCursorLabelName("Upper", 0);
    setCursorLabelName("Basis", 1);
    setCursorLabelName("Lower", 2);
    setDefaultBarFgColor(Color.blue, 0);    
    setDefaultBarFgColor(Color.red, 1);
    setDefaultBarFgColor(Color.blue, 2);
    setPlotType(PLOTTYPE_LINE,0);
    setPlotType(PLOTTYPE_LINE,1);
    setPlotType(PLOTTYPE_LINE,2);
    setDefaultBarThickness(1,0);
    setDefaultBarThickness(1,1);
    setDefaultBarThickness(1,2);
    var x=0;
    fpArray[x] = new FunctionParameter("Length", FunctionParameter.NUMBER);
	with(fpArray[x++]){
        setLowerLimit(1);		
        setDefault(10);
    }
     fpArray[x] = new FunctionParameter("Multiplier", FunctionParameter.NUMBER);
	with(fpArray[x++]){
        setLowerLimit(0);		
        setDefault(2);
    }
	fpArray[x] = new FunctionParameter("Source", FunctionParameter.STRING);
	with(fpArray[x++]){
        addOption("open"); 
        addOption("high");
        addOption("low");
        addOption("close");
        addOption("hl2");
        addOption("hlc3");
        addOption("ohlc4"); 
        setDefault("close"); 
    }
    fpArray[x] = new FunctionParameter("Type", FunctionParameter.BOOLEAN);
	with(fpArray[x++]){
        setName("Exponential");
        setDefault(false);
    }
	fpArray[x] = new FunctionParameter("Symbol", FunctionParameter.STRING);
    with(fpArray[x++]){
        setDefault();
	}
	fpArray[x] = new FunctionParameter("Interval", FunctionParameter.STRING);
	with(fpArray[x++]){
        setDefault();
    }
    fpArray[x] = new FunctionParameter("Offset", FunctionParameter.NUMBER);
	with(fpArray[x++]){
        setLowerLimit(0);
        setDefault(0);
    }
    fpArray[x] = new FunctionParameter("LineColor1", FunctionParameter.COLOR);
	with(fpArray[x++]){
        setName("Channel Color");
        setDefault(Color.blue);
    }
	fpArray[x] = new FunctionParameter("LineColor2", FunctionParameter.COLOR);
	with(fpArray[x++]){
        setName("Basis Color");
        setDefault(Color.red);
    }
    fpArray[x] = new FunctionParameter("Params", FunctionParameter.BOOLEAN);
	with(fpArray[x++]){
        setName("Show Parameters");
        setDefault(false);
    }
}

var bInit = false;
var vSymbol = null;
var xKeltner = null;
var xKeltnerBasis = null;
var xKeltnerUpper = null;
var xKeltnerLower = null;

function main(Length,Multiplier,Type,Source,Symbol,Interval,Offset,LineColor1,LineColor2,Params) {
    if(bInit == false){
        if(Symbol == null) Symbol = getSymbol();
        if(Interval == null) Interval = getInterval();
        vSymbol = Symbol+","+Interval;
        Type==false?Type=0:Type=1;
        xKeltner = efsInternal("calcKeltner",Type,Length,Multiplier,Offset,eval(Source),sym(vSymbol));
        xKeltnerUpper = getSeries(xKeltner,0);
        xKeltnerBasis = getSeries(xKeltner,1);
        xKeltnerLower = getSeries(xKeltner,2);
        setDefaultBarFgColor(LineColor1,0);
        setDefaultBarFgColor(LineColor2,1);
        setDefaultBarFgColor(LineColor1,2);
        setShowTitleParameters(eval(Params));
        bInit = true;
    }
    return new Array (xKeltnerUpper,xKeltnerBasis,xKeltnerLower);
}

var xInit = false;
var Avg = null;

function calcKeltner(type,length,multiplier,offset,source,series){
    if(xInit==false){
        if(type==0){
            Avg = offsetSeries(sma(length,source()),offset);
        }else if(type==1){
            Avg = offsetSeries(ema(length,source()),offset);
        }
        xInit=true;
    }       
	var AvgRange = 0;
    for(var i = 0; i < length; i++) {
		AvgRange += high(-(i+offset)) - low(-(i+offset));
	}
	AvgRange /= length;
	var Basis = Avg.getValue(0);
	var Upper = Basis+(AvgRange*multiplier);
	var Lower = Basis-(AvgRange*multiplier);
    return new Array (Upper,Basis,Lower);  
}