Strategy 2/20 Exponential Moving Average

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//  Copyright by HPotter v1.0 15/07/2014
// Strategy
// This indicator plots 2/20 exponential moving average. For the Mov 
// Avg X 2/20 Indicator, the EMA bar will be painted when the Alert criteria is met.
// You can use in the xPrice any series: Open, High, Low, Close, HL2, HLC3, OHLC4 and ect...
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study(title="Strategy 2/20 Exponential Moving Average", overlay = true)
Length = input(20, minval=1)
xPrice = close
xXA = ema(xPrice, Length)
nHH = max(high, high[1])
nLL = min(low, low[1])
nXS = iff((nLL > xXA)or(nHH < xXA), nLL, nHH)
pos = iff(close > xXA and close > nXS , 1,
	    iff(close < xXA and close < nXS, -1, nz(pos[1], 0))) 
barcolor(pos == -1 ? red: pos == 1 ? green : blue)
plot(nXS, color=blue, title="XAverage")