TFS: Volume Oscillator

/*********************************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:            TFS: Volume Oscillator     Version:            1.0  05/28/2009 Formula Parameters:                     Default:    AvgLen                              7    Notes:    This is the second part of TFS trading strategy. The concept of this     indicator is similar to that of On-Balance Volume indicator (OBV). It     is calculated according to these rules:    If Close > Open, Volume is positive    If Close < Open, Volume is negative    If Close = Open, Volume is neutral    Then you take the 7-day MA of the results. **********************************/var fpArray = new Array();var bInit = false;function preMain() {    setStudyTitle("TFS: Volume Oscilator");    setCursorLabelName("VolOsc",0);    setPlotType(PLOTTYPE_HISTOGRAM, 0);    setDefaultBarFgColor(Color.blue, 0);    addBand(0, PS_SOLID, 1, Color.red);    var x = 0;    fpArray[x] = new FunctionParameter("AvgLen", FunctionParameter.NUMBER);    with(fpArray[x++]) {        setLowerLimit(1);        setDefault(7);    }    }var xTFS_VolumeOsc = null;function main(AvgLen) {var nBarState = getBarState();var nTFS_VolumeOsc = 0;    if (nBarState == BARSTATE_ALLBARS) {        if (AvgLen == null) AvgLen = 7;    }    if (bInit == false) {        xTFS_VolumeOsc = efsInternal("Calc_TFS_VolumeOsc", AvgLen);        bInit = true;    }    nTFS_VolumeOsc = xTFS_VolumeOsc.getValue(0);    if (nTFS_VolumeOsc == null) return;    return nTFS_VolumeOsc;}var bSecondInit = false;var xClose = null;var xOpen = null;var xVolume = null;function Calc_TFS_VolumeOsc(AvgLen) {var nRes = 0;var i = 0;var nVolAccum = 0;    if (bSecondInit == false) {        xClose = close();        xOpen = open();        xVolume = volume();        bSecondInit = true;    }    if (xClose.getValue(-AvgLen) == null) return;    for (i = 0; i < AvgLen; i++) {        if (xClose.getValue(-i) > xOpen.getValue(-i)) nVolAccum += xVolume.getValue(-i);		if (xClose.getValue(-i) < xOpen.getValue(-i)) nVolAccum -= xVolume.getValue(-i);    }    nRes = nVolAccum / AvgLen;    return nRes;}