The Hilbert Transform is a technique used to generate inphase and quadrature components of a de-trended real-valued "analytic-like" signal (such as a Price Series) in order to analyze variations of the instantaneous phase and amplitude. HTTrendline (or MESA Instantaneous Trendline) returns the Price Series value after the Dominant Cycle of the analytic signal as generated by the Hilbert Transform has been removed. The Dominant Cycle can be thought of as being the "most likely" period (in the range of 10 to 40) of a sine function of the Price Series. The HTTrendline at a specific bar gives the current Hilbert Transform Trendline as instantaneously measured at that bar. In its Series form, the Instantaneous Trendline appears much like a Moving Average, but with minimal lag compared with the lag normally associated with such averages for equivalent periods. The HTTrendline is formed by removing the Dominant Cycle from the Price Series. See the examples.