Seasonal decomposition splits a series into trend, seasonality, and residuals

mdancho84 · x · 2026-07-22

Seasonal decomposition and STL

The post explains how seasonal decomposition splits a series into trend, seasonal, and residual components. It also defines STL as Seasonal-Trend-Loess, a flexible decomposition method that uses a LOESS smoother.

A key point is that STL can handle arbitrary seasonality rather than only fixed periodic patterns, and the residuals can be inspected for outliers after trend and seasonality are removed.

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