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We consider the problem of detecting anomalies in a large dataset. We propose a framework called Partial Identification which captures the intuition that anomalies are easy to distinguish from the overwhelming majority of points by…

Machine Learning · Computer Science 2019-12-10 Parikshit Gopalan , Vatsal Sharan , Udi Wieder

We make two contributions to the Isolation Forest method for anomaly and outlier detection. The first contribution is an information-theoretically motivated generalisation of the score function that is used to aggregate the scores across…

Machine Learning · Statistics 2023-09-21 Hichem Dhouib , Alissa Wilms , Paul Boes

Outlier detection has gained increasing interest in recent years, due to newly emerging technologies and the huge amount of high-dimensional data that are now available. Outlier detection can help practitioners to identify unwanted noise…

Statistics Theory · Mathematics 2021-05-20 Mads Lindskou , Torben Tvedebrink , Poul Svante Eriksen , Niels Morling

We propose a new method, named isolation Mondrian forest (iMondrian forest), for batch and online anomaly detection. The proposed method is a novel hybrid of isolation forest and Mondrian forest which are existing methods for batch anomaly…

Machine Learning · Computer Science 2021-11-02 Haoran Ma , Benyamin Ghojogh , Maria N. Samad , Dongyu Zheng , Mark Crowley

We describe the use of an unsupervised Random Forest for similarity learning and improved unsupervised anomaly detection. By training a Random Forest to discriminate between real data and synthetic data sampled from a uniform distribution…

Machine Learning · Statistics 2025-04-23 Joshua S. Harvey , Joshua Rosaler , Mingshu Li , Dhruv Desai , Dhagash Mehta

The Isolation Forest (iForest), proposed by Liu, Ting, and Zhou at TKDE 2012, has become a prominent tool for unsupervised anomaly detection. However, recent research by Hariri, Kind, and Brunner, published in TKDE 2021, has revealed issues…

Machine Learning · Computer Science 2025-01-30 Vahideh Monemizadeh , Kourosh Kiani

Random forests are a machine learning method used to automatically classify datasets and consist of a multitude of decision trees. While these random forests often have higher performance and generalize better than a single decision tree,…

Machine Learning · Computer Science 2025-07-31 Max Sondag , Christofer Meinecke , Dennis Collaris , Tatiana von Landesberger , Stef van den Elzen

For the purpose of monitoring the behavior of complex infrastructures (e.g. aircrafts, transport or energy networks), high-rate sensors are deployed to capture multivariate data, generally unlabeled, in quasi continuous-time to detect…

Machine Learning · Statistics 2019-10-10 Guillaume Staerman , Pavlo Mozharovskyi , Stephan Clémençon , Florence d'Alché-Buc

Random forests have become an established tool for classification and regression, in particular in high-dimensional settings and in the presence of complex predictor-response relationships. For bounded outcome variables restricted to the…

Methodology · Statistics 2019-01-21 Leonie Weinhold , Matthias Schmid , Marvin N. Wright , Moritz Berger

Random cut forest (RCF) algorithms have been developed for anomaly detection, particularly in time series data. The RCF algorithm is an improved version of the isolation forest (IF) algorithm. Unlike the IF algorithm, the RCF algorithm can…

Machine Learning · Computer Science 2024-01-10 Sijin Yeom , Jae-Hun Jung

We propose an algorithm named best-scored random forest for binary classification problems. The terminology "best-scored" means to select the one with the best empirical performance out of a certain number of purely random tree candidates…

Machine Learning · Statistics 2019-05-28 Hanyuan Hang , Xiaoyu Liu , Ingo Steinwart

Shared mobility systems, such as bike-sharing networks, play a crucial role in urban transportation. Identifying anomalies in these systems is essential for optimizing operations, improving service reliability, and enhancing user…

Machine Learning · Computer Science 2025-07-22 Elnur Isgandarov , Matteo Cederle , Federico Chiariotti , Gian Antonio Susto

Random Forests (RFs) are strong machine learning tools for classification and regression. However, they remain supervised algorithms, and no extension of RFs to the one-class setting has been proposed, except for techniques based on…

Machine Learning · Statistics 2016-11-22 Nicolas Goix , Nicolas Drougard , Romain Brault , Maël Chiapino

Anomaly detection is a fundamental problem in domains such as healthcare, manufacturing, and cybersecurity. This thesis proposes new unsupervised methods for anomaly detection in both structured and streaming data settings. In the first…

Machine Learning · Computer Science 2025-05-20 Filippo Leveni

Data mining offers a diverse toolbox for extracting meaningful structures from complex datasets, with anomaly detection emerging as a critical subfield particularly in the context of streaming or real-time data. Within anomaly detection,…

Machine Learning · Computer Science 2025-05-14 Adam Ulrich , Jan Krňávek , Roman Šenkeřík , Zuzana Komínková Oplatková , Radek Vala

We introduce an online outlier detection algorithm to detect outliers in a sequentially observed data stream. For this purpose, we use a two-stage filtering and hedging approach. In the first stage, we construct a multi-modal probability…

Machine Learning · Computer Science 2018-03-13 Mohammadreza Mohaghegh Neyshabouri , Suleyman Serdar Kozat

Recently, federated learning frameworks such as Python TestBed for Federated Learning Algorithms and MicroPython TestBed for Federated Learning Algorithms have emerged to tackle user privacy concerns and efficiency in embedded systems. Even…

Machine Learning · Computer Science 2025-09-05 Pavle Vasiljevic , Milica Matic , Miroslav Popovic

Random Forest (RF) is an ensemble classification technique that was developed by Breiman over a decade ago. Compared with other ensemble techniques, it has proved its accuracy and superiority. Many researchers, however, believe that there…

Machine Learning · Computer Science 2015-03-19 Khaled Fawagreh , Mohamad Medhat Gaber , Eyad Elyan

We address the problem of detecting anomalies with respect to structured patterns. To this end, we conceive a novel anomaly detection method called PIF, that combines the advantages of adaptive isolation methods with the flexibility of…

Machine Learning · Computer Science 2025-05-16 Filippo Leveni , Luca Magri , Giacomo Boracchi , Cesare Alippi

Random forests are a learning algorithm proposed by Breiman [Mach. Learn. 45 (2001) 5--32] that combines several randomized decision trees and aggregates their predictions by averaging. Despite its wide usage and outstanding practical…

Statistics Theory · Mathematics 2015-08-11 Erwan Scornet , Gérard Biau , Jean-Philippe Vert