[blackcat] L2 Ehlers HP-LP Roofing Filter

31 oct 2020

Level: 2

Background

John F. Ehlers introuced HP-LP Roofing Filter in his "Cycle Analytics for Traders" chapter 7 on 2013.


Function

A “roofing filter” can be used to limit the frequency content of an input before proceeding to construct an indicator. The roofing filter is composed of a highpass filter that passes only frequency components whose periods are shorter than 48 bars, for example. It also is composed of a SuperSmoother filter that passes frequency components whose periods are longer than 10 bars. Thus, the roofing filter is a wide bandwidth band-pass filter that passes only frequency components whose periods fall between 10 bars and 48 bars. This, by itself, is a simple indicator.

While the roofing filter indicator wiggles in proportion to the wiggles in the price data as you would expect, it is noticeable that the indicator is above zero for extended periods where the market is in an uptrend. In other words, the filter output does not have a zero mean as you would expect if the output consisted only of cyclic components whose periods fall between 10 bars and 48 bars.


Key Signal

Filt --> HP-LP Roofing Filter fast line
Trigger --> HP-LP Roofing Filter slow line

Pros and Cons

100% John F. Ehlers definition translation of original work, even variable names are the same. This help readers who would like to use pine to read his book. If you had read his works, then you will be quite familiar with my code style.

Remarks

The 41th script for Blackcat1402 John F. Ehlers Week publication.

Readme

In real life, I am a prolific inventor. I have successfully applied for more than 60 international and regional patents in the past 12 years. But in the past two years or so, I have tried to transfer my creativity to the development of trading strategies. Tradingview is the ideal platform for me. I am selecting and contributing some of the hundreds of scripts to publish in Tradingview community. Welcome everyone to interact with me to discuss these interesting pine scripts.

The scripts posted are categorized into 5 levels according to my efforts or manhours put into these works.

Level 1 : interesting script snippets or distinctive improvement from classic indicators or strategy. Level 1 scripts can usually appear in more complex indicators as a function module or element.

Level 2 : composite indicator/strategy. By selecting or combining several independent or dependent functions or sub indicators in proper way, the composite script exhibits a resonance phenomenon which can filter out noise or fake trading signal to enhance trading confidence level.

Level 3 : comprehensive indicator/strategy. They are simple trading systems based on my strategies. They are commonly containing several or all of entry signal, close signal, stop loss, take profit, re-entry, risk management, and position sizing techniques. Even some interesting fundamental and mass psychological aspects are incorporated.

Level 4 : script snippets or functions that do not disclose source code. Interesting element that can reveal market laws and work as raw material for indicators and strategies. If you find Level 1~2 scripts are helpful, Level 4 is a private version that took me far more efforts to develop.

Level 5 : indicator/strategy that do not disclose source code. private version of Level 3 script with my accumulated script processing skills or a large number of custom functions. I had a private function library built in past two years. Level 5 scripts use many of them to achieve private trading strategy.