D_DSP (Detrended Synthetic Price )

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//  Copyright by HPotter v1.0 25/06/2014
// Detrended Synthetic Price is a function that is in phase with the 
// dominant cycle of real price data. This DSP is computed by subtracting 
// a half-cycle exponential moving average (EMA) from the quarter cycle 
// exponential moving average.
// See "MESA and Trading Market Cycles" by John Ehlers pages 64 - 70. 
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study(title="D_DSP (Detrended Synthetic Price)", shorttitle="D_DSP (Detrended Synthetic Price)")
Length = input(14, minval=1)
hline(0, color=red, linestyle=line)
xHL2 = hl2
xEMA1 = ema(xHL2, Length)
xEMA2 = ema(xHL2, 2 * Length)
xEMA1_EMA2 = xEMA1 - xEMA2
plot(xEMA1_EMA2, color=blue, title="D_DSP")