This article introduces common recursive filters in TradeStation formulas, including FIR and IIR structures. It lists some common moving averages and filter types such as simple moving average, weighted moving average, exponential moving average, etc. Additionally, it mentions the principles and applications of the Kalman filter as a type of recursive filter. The article emphasizes that recursive filters are suitable for real-time systems and have the ability to adapt and adjust to changes in market conditions. Finally, it provides a list of common types and application areas for both recursive and non-recursive filters.