Outlier detection is an essential task in data mining, focused on identifying abnormal objects that deviate from normal distribution. The k-nearest neighbors-based detection method is one of the widely used techniques. However, as data scale increases, the process of finding k-nearest neighbors for each object becomes extremely time-consuming. Additionally, if neighbors of objects contain noise, it may interfere with computation of its relationships with neighbors, which affects detection performance. To address these issues, this paper proposes a fast and robust outlier detection method based on granular-ball (GB) center isolation and region consistency, called FROD. Specifically, generation of GBs is the first step. The dataset is covered by generating GBs with different granularities. Then, by calculating the GB center isolation (GBCI), it evaluates the isolation degree of different GB centers relative to other GB centers. From a global perspective, GBCI indirectly reflects the position and isolation of each GB center within the overall data distribution. Furthermore, by calculating the GB center region consistency (GBCRC) of an object, it measures closeness between object and GB center neighborhood. From a local perspective, GBCRC reflects the correlation between the object and the data distribution within the GB center neighborhood to which it belongs. Finally, by combining GBCI and GBCRC, outlier factor of each object is obtained, and a corresponding detection algorithm is designed. Experimental results show that FROD performs excellently in terms of detection efficiency and accuracy, and demonstrates robustness in noisy environments.
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