The Laguerre Filter (EHLLF) was created by John Ehlers. The EHLLF uses the last 4 prices to calculate its value. It also uses a factor called Gamma which is used to tune how much feedback is added to the result. The Laguerre Filter is an incredibly smooth filter. You can decrease the smoothing and the lag by decreasing Gamma. When the Gamma is reduced to zero, the Laguerre filter is identical to the FIR filter (a triangular weighted moving average).
This is a companion discussion topic for the original entry at https://www.optuma.com/kb/optuma/tools/ehlers/laguerre-filter