driftlast

Driftlast is a term used in data science and machine learning to describe the last observed data drift within a monitoring window of a data stream. It is not a standalone detection algorithm but a scalar or timestamp that summarizes the most recent distribution shift detected by a drift detector. The concept is sometimes used in discussions of model monitoring to complement more granular drift metrics such as feature-wise drift, population shift, or concept drift.

In practice, driftlast can be stored as the time or index of the most recent drift event, or as a short code summarizing its recency and magnitude. It is particularly relevant in systems that rely on timely retraining decisions: a recent driftlast can trigger a maintenance action, whereas a stale driftlast may indicate long periods of stability or a drift detector becoming unresponsive.

Relation to related concepts: driftlast is related to concept drift and data drift. Unlike detailed drift statistics, driftlast emphasizes recency rather than full distributional change, so it should be interpreted with caution and in context of other signals.

Limitations: driftlast provides limited information by itself and can be misleading if used without thresholding, window choices, or corroborating evidence. Its value depends on the detector's sensitivity and the chosen monitoring window.

See also: data drift, concept drift, model monitoring, drift detection.