The Volume-Weighted MACD Histogram

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//  Copyright by HPotter v1.0 29/08/2014
// The related article is copyrighted material from Stocks & Commodities 2009 Oct 
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study(title="Combining Exponential And Volume Weighting")
Long_period = input(26, minval=1)
Short_period = input(12, minval=1)
Smoothing_period = input(9, minval=1)
xLongMAVolPrice = ema(volume * close, Long_period) 
xLongMAVol = ema(volume, Long_period) 
xResLong = (xLongMAVolPrice * Long_period) / (xLongMAVol * Long_period)
xShortMAVolPrice = ema(volume * close, Short_period) 
xShortMAVol = ema(volume, Short_period) 
xResShort = (xShortMAVolPrice * Short_period) / (xShortMAVol * Short_period)
xVMACD = xResShort - xResLong
xVMACDSignal = ema(xVMACD, Smoothing_period)
nRes = xVMACD - xVMACDSignal
plot(nRes, color=blue, style = histogram )