McGinley Dynamic Convergence / Divergence [LazyBear]

//
// @author LazyBear
// List of all my indicators:
// https://docs.google.com/document/d/15AGCufJZ8CIUvwFJ9W-IKns88gkWOKBCvByMEvm5MLo/edit?usp=sharing
//
study(title="McGinley Dynamic Convergence/Divergence", shorttitle="MDCD_LB")
source = close
calc_mg(source, length) =>
    mg = na(mg[1]) ? ema(source, length) : mg[1] + (source - mg[1]) / (length * pow(source/mg[1], 4))
    mg

fastLength = input(12, minval=1), slowLength=input(26,minval=1)
signalLength=input(9,minval=1)
fastMA = calc_mg(source, fastLength)
slowMA = calc_mg(source, slowLength)
macd = fastMA - slowMA
signal = sma(macd, signalLength)
hist = macd - signal
plot(hist, color=red, style=histogram)
plot(macd, color=blue)
plot(signal, color=orange)