[RS]Modified McClellan Oscilator V0

study(title="[RS]Modified McClellan Oscilator V0")
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//  source: http://stockcharts.com/school/doku.php?id=chart_school:technical_indicators:mcclellan_oscillator
//  Ratio Adjusted Net Advances (RANA): (Advances - Declines)/(Advances + Declines)
//
//    McClellan Oscillator: 19-day EMA of RANA - 39-day EMA of RANA
//
//  19-day EMA* = (Current Day RANA - Prior Day EMA) * .10 + Prior Day EMA)
//  39-day EMA* = (Current Day RANA - Prior Day EMA) * .05 + Prior Day EMA)
//
//  * The first EMA calculation is a simple average. 
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fast_length = input(title='EMA - Fast Length:', type=integer, defval=19)
slow_length = input(title='EMA - Slow Length:', type=integer, defval=39)
USE_RANA = input(title='Use Ratio Adjustment Net Advancement:', type=bool, defval=true)

advance = cum(close > open ? close - open : 0)
decline = cum(close < open ? open - close : 0)

adv_dec = USE_RANA ? ((advance-decline)/(advance+decline)) : change(close)
ma_fast = ema(adv_dec, fast_length)
ma_slow = ema(adv_dec, slow_length)

mcl_osc = ma_fast-ma_slow
plot(mcl_osc)
hline(0, color=black)