VERSION INFORMATION

PSI_DRIFT.java is deprecated

PSI_DRIFT_A.java -> Landmark Windows

PSI_DRIFT_B.java -> Sliding Windows

POPULATION STABILITY INDEX DETECTOR METHOD

m_n : counts number of instances

minNumInstances : grace_period - Number of skipped instances before starts the drift detector

numBins : sets the number of bins in each window distributions. Defaults to 10 bins.

instancesPerDistribution : sets the nuber of instances per distributions windows. Defaults to 100 instances.

warningLevel : sets the threshold to trigger warning alarm. Defaults to 10%

outcontrolLevel : sets the threshold to trigger drift detection. Defaults to 20%.

HOW THE PSI DRIFT DETECTOR METHOD WORKS

i.Sliding Window

1. Two LinkedLists, firstWindow and secondWindow, are used to store the instances of the current and previous distributions.

2. The resetLearning() method initializes the member variables to their default values.

3. The input(double prediction) method is called for each new prediction in the data stream. It increments the instance count (m_n) and performs the following steps:

   a. If the instance count is less than or equal to the number of instances per distribution, the prediction is added to the firstWindow and the method returns.

   b. If the instance count exceeds the number of instances per distribution, the prediction is added to the secondWindow.

   c. If the size of the secondWindow is less than the number of instances per distribution, the method returns.

   d. The computePSI() method is called to calculate the PSI between the firstWindow and secondWindow.

   e. The updateDetectionStatus() method updates the detection status based on the calculated PSI value.

   f. The oldest instance is removed from the firstWindow, and the first instance from the secondWindow is added to the firstWindow.

4. The computePSI(List<Double> expected, List<Double> actual, int numBins) method calculates the PSI measure between two distributions (expected and actual) using the specified number of bins. It computes the histogram of each distribution, normalizes the histograms, and then calculates the PSI value based on the normalized histograms.

5. The updateDetectionStatus(double psi) method updates the detection status based on the calculated PSI value. It sets the estimation field to the PSI value, determines if a change or warning is detected based on the warning and outcontrol levels, and updates the corresponding fields (isChangeDetected, isWarningZone, and delay).