ARIMA and SARIMA Models
AR, MA, I components, parameter selection with ACF/PACF, statsmodels ARIMA fitting.
What Is ARIMA?
ARIMA stands for AutoRegressive Integrated Moving Average. It models a stationary series using three parts: autoregression (p), integration/differencing (d), and a moving average of errors (q), written as ARIMA(p, d, q).
AR(p): Autoregressive
The AR term predicts the next value from a linear combination of its own p previous values. If today depends strongly on the last few days, you need a nonzero p.
Example: p=2 uses the two most recent observations as predictors.