Adaptive Bandpass Filter [Ehlers]

4 Feb 2019

This is my latest bandpass filter - used to determine if a security is in a trend or cycle.
Now with an adaptive period setting! I use Ehlers in-phase & quadrature dominant cycle measurement (IQ IFM) method to set the period dynamically.
This method favors longer periods which tend to produce smoother, albeit laggier bandpass oscillator plots. From my quick tests, I tend to have lag between 4 and 8 bars, depending on the Timeframe.
The lower timeframes tend to have more noise and thus produce more interfering frequencies that may cause lag.

>Settings

• Source: Select the data source to perform calc's on (close, open, etc...)
  
• Period: Select the period to tune. Periods outside of this value will be attenuated (reduced)
  
• Adaptive: Enable to have the I-Q IFM set the period for you (disables Period setting)
  
• Bandpass Tolerance: Allow periods that are plus/minus the chosen period to pass.
  
• Cycle Tolerance: Sensitivity of cycle mode. Lower values consider trends more frequent, higher values consider cycles more frequent.
  

Bandpass tolerance example: for instance, if this setting is 0.1 (10%) and Period is set to 20, then waves with a period of 18 - 22 will pass.

>How to read

• Red line is the bandpass output, showing a lagged version of the dominant cycle representing the
  
• Black lines are the upper and lower bounds for a cycle
  
• Green Background indicates an uptrend
  
• Red background indicates a downtrend