This is the Laguerre Filter described in Chapter 14.  Ehlers describes this filter as a balance between smoothing a signal and lag in order to avoid whipsaw trades.

PriceIn = defaults to Close but change to the Price indicator to match the book

Gamma = defaults to 0.8 as described in the book.

For more information on this indicator, refer to Chapter 14 of "Cybernetic Analysis for Stocks and Futures" by John Ehlers, Publisher: John Wiley & Sons; (March 19, 2004), ISBN: 0471463078