Accerelation and Speed Ver 1.1 for eSignal (EFS)

/*********************************
Provided By:  
    eSignal (Copyright c eSignal), a division of Interactive Data 
    Corporation. 2009. 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:        
    Acceleration & Speed
Version:            1.0  09/25/2009
 
Formula Parameters:                     Default:
    Length                              24
    sPrice                              Close
    
Notes:
    
**********************************/
var fpArray = new Array();
var bInit = false;

function preMain(){
    setPriceStudy(false);
    setShowCursorLabel(true);
    setShowTitleParameters(false);
    setStudyTitle("Acceleration & Speed");
    setCursorLabelName("Speed", 0);
    setPlotType(PLOTTYPE_LINE, 0);
    setDefaultBarFgColor(Color.red, 0);
    setCursorLabelName("Acceleration", 1);
    setPlotType(PLOTTYPE_LINE, 1);
    setDefaultBarFgColor(Color.green, 1);
    var x = 0;
    fpArray[x] = new FunctionParameter("Length", FunctionParameter.NUMBER);
    with(fpArray[x++]) {
        setLowerLimit(1);
        setDefault(24);
    }    
    fpArray[x] = new FunctionParameter("sPrice", FunctionParameter.STRING);
	with(fpArray[x++]){
        setName("Source of Price");
        addOption("open"); 
        addOption("high");
        addOption("low");
        addOption("close");
        addOption("hl2");
        addOption("hlc3");
        addOption("ohlc4"); 
        setDefault("close"); 
    }    
}

var xSpeed = null;
var xAcceleration = null;

function main(Length, sPrice) {
var nBarState = getBarState();
var nSpeed = 0;
var nAcceleration = 0;
    if (nBarState == BARSTATE_ALLBARS) {
        if(Length == null) Length = 2;
        if(sPrice == null) sPrice = "close";
	}
	if (bInit == false) {
        xSpeed = mom(Length, eval(sPrice)());
        xAcceleration = mom(Length, xSpeed);
        bInit = true;
	}
    nSpeed = xSpeed.getValue(0);
    nAcceleration = xAcceleration.getValue(0);
    if (nAcceleration == null) return;
    return new Array(nSpeed, nAcceleration);
}