The Chart Pattern Trader
The Extreme Point Rule
The directional movement indicator is a powerful tool for spotting shifts in market momentum. A buy signal is given when the positive directional indicator ( DI) crosses above the negative directional indicator (-DI), and conversely, when negative directional indicator crosses above the positive directional indicator a sell signal is generated. When the market is trendless the DI lines crisscross back and forth, which can generate false signals.
Solely following the DI and -DI cross signals by themselves can lead to whipsaws and overtrading. Steven Achelis offers a solution to this problem using the 'extreme point rule' in his marvelous book, Technical Analysis From A To Z. Achelis points to the creator of the directional movement system J. Welles Wilder, and his simple trading rule, to help prevent whipsaws and reduce the number of signals that a trader acts upon.
The extreme point rule requires a trader to mark the extreme price point the day in which the DI and -DI cross. According to Achelis, the extreme point is highest of point of a session when DI crosses above -DI and is the lowest point of the session when -DI crosses above DI. Buy or sell signals are triggered when prices move beyond the extreme point.