Bill Williams. Awesome Oscillator (AC) Signal Line

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//  Copyright by HPotter v2.0 18/09/2014
//    This indicator plots the oscillator as a histogram where blue denotes 
//    periods suited for buying and red . for selling. If the current value 
//    of AO (Awesome Oscillator) is above previous, the period is considered 
//    suited for buying and the period is marked blue. If the AO value is not 
//    above previous, the period is considered suited for selling and the 
//    indicator marks it as red.
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study("Bill Williams. Awesome Oscillator (AC) with Signal Line")
nLengthSlow = input(34, minval=1, title="Length Slow")
nLengthFast = input(5, minval=1, title="Length Fast")
nLengthMA = input(15, minval=1, title="MA")
nLengthEMA = input(15, minval=1, title="EMA")
nLengthWMA = input(15, minval=1, title="WMA")
bShowWMA = input(type=bool, defval=true, title="Show WMA")
bShowMA = input(type=bool, defval=false, title="Show MA")
bShowEMA = input(type=bool, defval=false, title="Show EMA")
xSMA1_hl2 = sma(hl2, nLengthFast)
xSMA2_hl2 = sma(hl2, nLengthSlow)
xSMA1_SMA2 = xSMA1_hl2 - xSMA2_hl2
xSMA_hl2 = sma(xSMA1_SMA2, nLengthFast)
nRes =  xSMA1_SMA2 - xSMA_hl2
xResWMA = wma(nRes, nLengthWMA)
xResMA = sma(nRes, nLengthMA)
xResEMA = ema(nRes, nLengthEMA)
cClr = nRes > nRes[1] ? blue : red
plot(bShowWMA ? xResWMA : na, color = green)
plot(bShowMA ? xResMA : na, color = green)
plot(bShowEMA ? xResEMA : na, color = green)
plot(nRes, style=histogram, linewidth=1, color=cClr)