/*********************************************************
Alexis C. Montenegro © March 2006                         
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("Acceleration Bands");
    setCursorLabelName("Upper",0);
    setCursorLabelName("Mid",1);
    setCursorLabelName("Lower",2);
    setDefaultBarFgColor(Color.blue,0);
    setDefaultBarFgColor(Color.black,1);
    setDefaultBarFgColor(Color.red,2);
    var x=0;
    fpArray[x] = new FunctionParameter("Length", FunctionParameter.NUMBER);
	with(fpArray[x++]){
        setLowerLimit(1);		
        setDefault(20);
    }
	fpArray[x] = new FunctionParameter("Interval", FunctionParameter.STRING);
	with(fpArray[x++]){
        setDefault();
    }
    fpArray[x] = new FunctionParameter("Params", FunctionParameter.BOOLEAN);
	with(fpArray[x++]){
        setName("Show Parameters");
        setDefault(false);
    }
}

var bInit = false;
var vInterval = null;
var xBands = null;
var xBasis = null;
var xUpper = null;
var xLower = null;

function main(Length,Interval,Params){
    if(bInit==false){
        if(Interval == null) Interval = getInterval();
        var vInterval = Interval;
        xBands = efsInternal("calcBands",Length,inv(vInterval));
        xBasis = getSeries(xBands,0);
        xUpper = getSeries(sma(Length,getSeries(xBands,1)));
        xLower = getSeries(sma(Length,getSeries(xBands,2)));
        setShowTitleParameters(eval(Params));
        bInit=true;
    }
    return new Array (xUpper,xBasis,xLower);
}

var xInit = false;
var xAvg = null;
var xHigh = null;
var xLow = null;

function calcBands(length,interval){
    if(xInit==false){
        xAvg = sma(length);
        xHigh = high();
        xLow = low();
        xInit=true;
    }
    var vH = xHigh.getValue(0);
    var vL = xLow.getValue(0);
    if(vH == null || vL == null) return;
    var vCalc1 = ((vH*(1+2*(((vH-vL)/((vH+vL)/2))*1000)*.001)));
    var vCalc2 = ((vL*(1-2*(((vH-vL)/((vH+vL)/2))*1000)*.001)));  
    return new Array (xAvg.getValue(0),vCalc1,vCalc2);
}