Plots linear regression "line of best fit" for a given source and length. Also plots the standard deviation of residuals as upper and lower bands. For some reason it's not plotting the lines exactly where the values are, so I wouldn't recommend using it as a purely visual indicator, but it could be used in strategies. A quick implementation of a strategy buying...
Bull and Bear power based on linear regression (this is a non lagging oscillator, the parameter are for the lookup window for the donchian extremes)
this indicator can also be used for convergence/divergence.