Modified Donchian.pine

//@version=4
study(title="Donchian Channels Experiment", shorttitle="DC Exp", overlay=true, resolution="")
donchianChannelSource = input(title="Donchian Channel Source", defval="High/Low", options=["Close/Open", "High/Low"])
donchianChannelLength = input(100, minval=1)

lower = lowest(donchianChannelLength)
donchianLowest = if donchianChannelSource == "Close/Open"
    lowestopen  = lowest(open, donchianChannelLength)
    lowestclose = lowest(close, donchianChannelLength)
    lower := if lowestopen < lowestclose
        lowestopen
    else
        lowestclose

upper = highest(donchianChannelLength)
donchianHighest = if donchianChannelSource == "Close/Open"
    highestopen  = highest(open, donchianChannelLength)
    highestclose = highest(close, donchianChannelLength)
    upper := if highestopen > highestclose
        highestopen
    else
        highestclose

basis = avg(upper, lower)
plot(basis, "Basis", color=#FF6D00)
l = plot(lower, "Lower", color=#2962FF)
u = plot(upper, "Upper", color=#2962FF)
// fill(u, l, color=color.rgb(33, 150, 243, 95), title="Background")