2008 Apr: RSI Bands, by François Bertrand

[eSignal_JasonK]

File Name: RSI_Bands.efs

Description:
These studies are based on the April 2008 article, RSI Bands, by François Bertrand.

Formula Parameters:
Periods: 14
Upper Band: 70
Lower Band: 30
Band Color: Blue
Band Thickness: 2
Enable Clamping: false

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

Download File:
RSI_Bands.efs



EFS Code:

/*********************************
Provided By:  
    eSignal (Copyright © eSignal), a division of Interactive Data 
    Corporation. 2007. 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:        RSI Bands
                    by François Bertrand

Version:            1.0  2/5/2008

Notes:
* April 2008 Issue of Stocks and Commodities Magazine
* Study requires version 8.0 or later.

Formula Parameters:                 Defaults:
Periods                             14
Upper Band                          70
Lower Band                          30
Band Color                          Blue
Band Thickness                      2
Enable Clamping                     false
**********************************/


function preMain() {
    setPriceStudy(true);
    setStudyTitle("RSI Bands ");
    setCursorLabelName("RSIB70", 0);
    setCursorLabelName("RSIB30", 1);
    setShowTitleParameters(false);

    var fp1 = new FunctionParameter("nPeriods", FunctionParameter.NUMBER);
        fp1.setName("Periods");
        fp1.setLowerLimit(0);
        fp1.setDefault(14);
    var fp2 = new FunctionParameter("nUpper", FunctionParameter.NUMBER);
        fp2.setName("Upper Band");
        fp2.setLowerLimit(0);
        fp2.setDefault(70);
    var fp3 = new FunctionParameter("nLower", FunctionParameter.NUMBER);
        fp3.setName("Lower Band");
        fp3.setLowerLimit(0);
        fp3.setDefault(30);
    var fp4 = new FunctionParameter("cColor", FunctionParameter.COLOR);
        fp4.setName("Band Color");
        fp4.setDefault(Color.blue);
    var fp5 = new FunctionParameter("nThick", FunctionParameter.NUMBER);
        fp5.setName("Band Thickness");
        fp5.setLowerLimit(1);
        fp5.setDefault(2);
    var fp6 = new FunctionParameter("bClamp", FunctionParameter.BOOLEAN);
        fp6.setName("Enable Clamping");
        fp6.setDefault(false);
}


// Global Variables
var bVersion  = null;    // Version flag
var bInit     = false;   // Initialization flag

var xUpperRSI = null;
var xLowerRSI = null;

function main(nPeriods, nUpper, nLower, cColor, nThick, bClamp) {
    var nState = getBarState();
    var nIndex = getCurrentBarIndex();
    if (bVersion == null) bVersion = verify();
    if (bVersion == false) return;    
    
    
    if (bInit == false) {
        setStudyTitle("RSI Bands (" + nPeriods + ", " + nUpper + ", " + nLower + ")");
        setCursorLabelName("RSIB"+nUpper, 0);
        setCursorLabelName("RSIB"+nLower, 1);
        setDefaultBarFgColor(cColor, 0);
        setDefaultBarFgColor(cColor, 1);
        setDefaultBarThickness(nThick, 0);
        setDefaultBarThickness(nThick, 1);
        
        xUpperRSI = efsInternal("RSI_Band", nPeriods, nUpper, bClamp );
        xLowerRSI = efsInternal("RSI_Band", nPeriods, nLower, bClamp );
        
        bInit = true;
    }
    
    var nUpperRSI = xUpperRSI.getValue(0);
    var nLowerRSI = xLowerRSI.getValue(0);
    if (nUpperRSI == null || nLowerRSI == null) return;
    
    return new Array(nUpperRSI, nLowerRSI);    
}


var result = null;
var result_1 = null;
var P = 0;
var N = 0;
var P_1 = 0;
var N_1 = 0;

function RSI_Band( period, TargetRSILevel, clamp ) {
    var diff = null;
    var HypotheticalCloseToMatchRSITarget = 0;
    var nState = getBarState();

    if (nState == BARSTATE_NEWBAR) {
        result_1 = result;
        P_1 = P;
        N_1 = N;
    }
    
    if (close(-period) == null) return;

    var W = 0;
    var S = 0;
    var diff = close(0) - close(-1);
    if( diff > 0 ) W = diff;
    if( diff < 0 ) S = -diff;
    // Compute the hypothetical price close to reach the target RSI level
    // based on yesterday’s RSI and close
    // Depending on if we would need the price to increase or decrease,
    // we use a different formula
    if (result_1 != null && result_1 > close(-1)) {
        HypotheticalCloseToMatchRSITarget = close(-1)+P_1-P_1*period-((N_1*period)-N_1)*TargetRSILevel /(TargetRSILevel - 100);
    } else {
        HypotheticalCloseToMatchRSITarget = close(-1)-N_1-P_1+N_1*period+P_1*period+(100*P_1)/TargetRSILevel -(100*P_1*period)/TargetRSILevel;
    }
    
    if (clamp == true) {
        // Optional clamping code
        // Enable the clamping option in Edit Studies if parameters used cause too much volatility.
        // (generally caused by using a very short period) This will keep the RSI Bands
        // within roughly 10% of the price
        if ( (HypotheticalCloseToMatchRSITarget - close(-1)) > 0.1*close(-1)) {
            HypotheticalCloseToMatchRSITarget = close(-1)*1.1;
        } else if ( (HypotheticalCloseToMatchRSITarget - close(-1)) < -0.1*close(-1)) {
            HypotheticalCloseToMatchRSITarget = close(-1)*0.9;
        }
        // Resume standard RSI code to update the running P and N averages
    }
    
    P = ( ( period -1 ) * P_1 + W ) / period;
    N = ( ( period -1 ) * N_1 + S ) / period;

    if (getCurrentBarCount() >= period) {
        result = HypotheticalCloseToMatchRSITarget;
        return result;
    } else {
        return null;
    }
}


function verify() {
    var b = false;
    if (getBuildNumber() < 779) {
        drawTextAbsolute(5, 35, "This study requires version 8.0 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;
}