Advance-Decline Indicator

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//  Copyright by HPotter v1.0 08/09/2014
// The Advance-Decline Indicator is a market breadth indicator 
// based on the smoothed difference between advancing and declining issues.
// The indicator shows when the stock market is overbought (and a correction 
// is due) and when it is oversold (and a rally is due).
// The Advance-Decline Indicator is a 10-period exponential moving average of 
// the difference between the number of advancing and declining issues.
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study(title="Advance-Decline Indicator")
Length = input(10, minval=1)
BuyBand = input(-1500)
SellBand = input(1500, minval=1)
hline(SellBand, color=red, linestyle=line)
hline(BuyBand, color=green, linestyle=line)
xOvbOvs = ema(close, Length)
clr = iff(high > SellBand, red, iff(low < BuyBand, green, blue))
plot(xOvbOvs, color = clr, style  = histogram, linewidth = 2, title="Advance-Decline Indicator")