// RSI Bands use a variation of the RSI calculations to figure
// out what price level a stock should be at to be considered
// overbought/oversold.
//
// This sample code was built off the "BuiltInRSIEquivalent"
// sample RSI calculation code found on the AmiBroker website.
function BuiltInRSIEquivalent_RSI_Band_Version( period, TargetRSILevel )
{
    P = N = 0;
    result = Null;
    for( i = 1; i < BarCount; i++ )
    {
        // Standard RSI code
        diff = C[ i ] - C[ i - 1 ];
        W = S = 0;
        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 whether we would need the price to
// or decrease, we use a different formula
        if(result[i-1] > C[i-1])
            HypotheticalCloseToMatchRSITarget = C[i-1]+P-P*period-((N*period)-N)
                                                *TargetRSILevel/(TargetRSILevel -100);
        else
            HypotheticalCloseToMatchRSITarget = C[i-1]-N-P+N*period+P*period+(100*P)
                                                /TargetRSILevel-(100*P*period)/TargetRSILevel ;
        // Optional clamping code
        // Uncomment this section 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 - C[i]) > 0.1*C[i])
        // HypotheticalCloseToMatchRSITarget = C[i]*1.1;
        // if( (HypotheticalCloseToMatchRSITarget - C[i]) < - 0.1*C[i])
        // HypotheticalCloseToMatchRSITarget = C[i]*0.9;
        // Resume standard RSI code to update the
        // running P and N averages
        P = ( ( period -1 ) * P + W ) / period;
        N = ( ( period -1 ) * N + S ) / period;
        // Store result
        if( i >= period )
            result[ i ] = HypotheticalCloseToMatchRSITarget ;
    }
    return result;
}
Plot( BuiltInRSIEquivalent_RSI_Band_Version(14,80), "RSIB80", colorBlue );
Plot( BuiltInRSIEquivalent_RSI_Band_Version(14,20), "RSIB20", colorBlue );

//--François Bertrand