Scalper's Channel

//
// @author LazyBear
// @credits http://freethinkscript.blogspot.com/2009/05/only-scalpers-channel-that-you-will.html
//
study(title = "Scalper's Channel [LazyBear]", shorttitle="weak_volume_dependency [LB]", overlay=true)
length = input(20)
factor = input(15)
pi = atan(1)*4
Average(x,y) => (sum(x,y) / y)
scalper_line= plot(Average(close, factor) - log(pi * (atr(factor))), color=blue, linewidth=3)
hi = plot (highest(length), color=fuchsia)
lo = plot (lowest(length), color=fuchsia)