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ADWIN

Adaptive Windowing method for concept drift detection.

ADWIN (ADaptive WINdowing) is a popular drift detection method with mathematical guarantees. ADWIN efficiently keeps a variable-length window of recent items; such that it holds that there has no been change in the data distribution. This window is further divided into two sub-windows \((W_0, W_1)\) used to determine if a change has happened. ADWIN compares the average of \(W_0\) and \(W_1\) to confirm that they correspond to the same distribution. Concept drift is detected if the distribution equality no longer holds. Upon detecting a drift, \(W_0\) is replaced by \(W_1\) and a new \(W_1\) is initialized. ADWIN uses a confidence value \(\delta=\in(0,1)\) to determine if the two sub-windows correspond to the same distribution.

Input: value can be any numeric value related to the definition of concept change for the data analyzed. For example, using 0's or 1's to track drift in a classifier's performance as follows:

  • 0: Means the learners prediction was wrong

  • 1: Means the learners prediction was correct

Parameters

  • delta – defaults to 0.002

    Confidence value.

Attributes

  • change_detected

    Concept drift alarm. True if concept drift is detected.

  • delta

  • estimation

    Error estimation

  • n_detections

  • total

  • variance

  • warning_detected

    Warning zone alarm. Indicates if the drift detector is in the warning zone. Applicability depends on each drift detector implementation. True if the change detector is in the warning zone.

  • width

    Window size

Examples

>>> import random
>>> from river import drift

>>> rng = random.Random(12345)
>>> adwin = drift.ADWIN()

>>> # Simulate a data stream composed by two data distributions
>>> data_stream = rng.choices([0, 1], k=1000) + rng.choices(range(4, 8), k=1000)

>>> # Update drift detector and verify if change is detected
>>> for i, val in enumerate(data_stream):
...     in_drift, _ = adwin.update(val)
...     if in_drift:
...         print(f"Change detected at index {i}, input value: {val}")
...         adwin.reset()  # Good practice
Change detected at index 1023, input value: 4

Methods

clone

Return a fresh estimator with the same parameters.

The clone has the same parameters but has not been updated with any data. This works by looking at the parameters from the class signature. Each parameter is either - recursively cloned if it's a River classes. - deep-copied via copy.deepcopy if not. If the calling object is stochastic (i.e. it accepts a seed parameter) and has not been seeded, then the clone will not be idempotent. Indeed, this method's purpose if simply to return a new instance with the same input parameters.

reset

Reset the change detector.

update

Update the change detector with a single data point.

Apart from adding the element value to the window, by inserting it in the correct bucket, it will also update the relevant statistics, in this case the total sum of all values, the window width and the total variance.

Parameters

  • value (numbers.Number)

Returns

typing.Tuple[bool, bool]: tuple

References

  1. Albert Bifet and Ricard Gavalda. "Learning from time-changing data with adaptive windowing." In Proceedings of the 2007 SIAM international conference on data mining, pp. 443-448. Society for Industrial and Applied Mathematics, 2007. ↩