Adaptive Donchian Channel

This indicator adds a level of adaptivity to the simple Donchian Channel by adjusting the sensitivity (lookback periods) of the channel's upper and lower bounds based on the amount of time that has elapsed since the price has hit/expanded the channel boundaries. Comparing the results of this indicator to the standard Donchian Channel, the readier level of responsiveness may prove self-evident.

METHODOLOGY:
Specifically, the more recently the channel was expanded in one direction, the longer the lookback period grows in that direction. Conversely, if the channel has not been expanded in a given direction, the lookback period will contract so as to allow for a tighter channel.

For example, let the initial lookback period be 20 bars and let the factor argument be 0.1 (or 2 bars to start, as 20*0.1 = 2). Now say the current bar sets a new 20-period high. Then the lookback period for the upper bound is expanded by 2 bars to 22, and the lookback period for the lower bound is contracted by 2 bars to 18, thereby making it simultaneously harder to set new highs and easier to set new lows (and vice versa for hitting new lows). If neither a new high nor a new low is formed, both periods contract by the given factor.