The Aroon indicator by Tushar Chande shows the length of time since the highest or lowest close among the past N days’ closes. There are three lines: Aroon Up for the high, Aroon Down for the low, and the Aroon Oscillator.
Aroon Up and Down are both expressed as percentages 0 to 100. If today is a new N-day high then Aroon Up is 100, and for each day that passes (without a fresh N-day high) it drops by 100/N, down to 0 for no new highs in the past N days. Conversely for Aroon Down for new N-day lows.
The Aroon Oscillator is simply the difference between the Up and Down lines,
AroonOsc = AroonUp - AroonDown
In Chart the Up line is drawn in green, the down in red, and the oscillator in white.
Copyright 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2014, 2015, 2016, 2017 Kevin Ryde
Chart is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.