This is an indicator adapted from a C# implementation for cTrader. It is a simple linear IIR filter. The indicator is widely available for MetaTrader 4 in Forex fora, but I have not checked the C# version against the original mq4 files.
When price is above the Coral filter, only consider a long position. When price is below the indicator, only consider a short position.
Detailed information on the indicator is available here:
The indicator comes with a trend indication based on the slope of the linear filter. The neutral range can be adjusted via the threshold parameter. The trend can be displayed via paintbars. The trend state is exposed via an IntSeries() and be directly called from a strategy.
The filter follows the EasyLanguage code, which you will find under Figure 6 in the paper cited above. However, it uses a 4-period triangular moving average as input series, where the code example relies on the bar center.
The Distance Coefficient Ehlers Filter is already included with the Bollinger Bands Universal, Keltner Channel Universal, SuperTrend U11 and Heikin Ashi indicators, but I had not made it available so far as a separate download.
Update October 1, 2012: Small bug removed. Indicator will now correctly display when a period of 1 is selected.
This indicator is ported from on FatTails' Kaufman Efficiency Ratio indicator for NinjaTrader 7.
The Kaufman Efficiency Ratio shows the amount of "trendiness" versus chop. When the Efficiency Ratio crosses above the chop line, there is a trend. If the Efficiency Ratio crosses below that, the market is range bound.
Efficiency Ratio's above the horizontal chop line cause this line to be coloured yellow to help with the interpretation of chop vs trend.
This is a collection of various filters by John Ehlers outlined in his books "Rocket Science for Traders" and "Cybernet Analysis for Stocks and Futures".