DBSCAN is a density-based clustering algorithm that identifies dense regions and permits some observations to remain outside every cluster. For outlier detection, clustered points are treated as inliers, while unclustered points receive the outlier label. section 3.2.3
A practical DBSCAN outlier-detection workflow is:
- Prepare the data by replacing nulls, encoding categorical columns, and scaling numeric features when necessary. section 3.2.3
- Inspect different eps values because one setting can flag too many or too few records. section 4.11
- Compare DBSCAN with other detectors and manually assess whether flagged records are substantively interesting. section 4.11
Dataset applications
Using V6 and V19 from the wall-robot-navigation dataset produces three major clusters and several unclustered points flagged as outliers. On scaled baseball data, setting eps to 2.0 yields 1,255 inliers and 85 outliers; repeatedly varying eps creates a more graded DBSCAN score.


