> "Wilder didn't like standard EMA weighting. He wanted history to decay slower. So he invented RMA, which is just EMA with a different alpha, confusing traders for 40 years."
The Running Moving Average (RMA), also known as the Smoothed Moving Average (SMMA) or Wilder's Moving Average, is the backbone of J. Welles Wilder's most famous indicators: RSI, ATR, and ADX. It is functionally identical to an Exponential Moving Average (EMA), but with a smoothing factor ($\alpha$) of $1/N$ instead of $2/(N+1)$. This results in a longer "memory" and slower decay than a standard EMA of the same period.
Introduced by J. Welles Wilder Jr. in his seminal 1978 book, *New Concepts in Technical Trading Systems*. Wilder developed his systems on a programmable calculator (the HP-67), where memory was scarce. The RMA allowed him to update averages without storing a history buffer, using a simple recursive formula. It remains the standard smoothing method for RSI and ATR.
RMA is an infinite impulse response (IIR) filter. In QuanTAlib, `Rma` is implemented as a zero-cost wrapper around the `Ema` class. It simply instantiates an `Ema` with a modified alpha.
1.**Initialization**: Like EMA, RMA requires a "warmup" period to converge. Wilder often initialized with a Simple Moving Average (SMA) of the first $N$ bars. QuanTAlib follows this convention.
2.**Naming**: Often called SMMA (Smoothed Moving Average) in other libraries.
3.**Period Mismatch**: Using an EMA(14) where an RMA(14) is expected will result in a much faster-moving line (equivalent to RMA(7.5)).
