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Outlier detection is a significant area in data mining. It can be either used to pre-process the data prior to an analysis or post the processing phase (before visualization) depending on the effectiveness of the outlier and its importance.…

Machine Learning · Statistics 2021-06-22 Jacob John

Outlier detection is a core task in data mining with a plethora of algorithms that have enjoyed wide scale usage. Existing algorithms are primarily focused on detection, that is the identification of outliers in a given dataset. In this…

Machine Learning · Computer Science 2019-11-11 Yue Wu , Leman Akoglu , Ian Davidson

Outlier detection aims to identify unusual data instances that deviate from expected patterns. The outlier detection is particularly challenging when outliers are context dependent and when they are defined by unusual combinations of…

Artificial Intelligence · Computer Science 2015-05-18 Charmgil Hong , Milos Hauskrecht

In statistics and machine learning, the traditional meaning of the terms `outlier' and `anomaly' is a case in the dataset that behaves differently from the bulk of the data. This raises suspicion that it may belong to a different…

Methodology · Statistics 2026-04-17 Mia Hubert , Jakob Raymaekers , Peter J. Rousseeuw

Outlier detection and cleaning are essential steps in data preprocessing to ensure the integrity and validity of data analyses. This paper focuses on outlier points within individual trajectories, i.e., points that deviate significantly…

Databases · Computer Science 2025-11-26 Mariana M Garcez Duarte , Mahmoud Sakr

The isolation forest algorithm for outlier detection exploits a simple yet effective observation: if taking some multivariate data and making uniformly random cuts across the feature space recursively, it will take fewer such random cuts…

Machine Learning · Statistics 2021-11-24 David Cortes

The neighbor-based method has become a powerful tool to handle the outlier detection problem, which aims to infer the abnormal degree of the sample based on the compactness of the sample and its neighbors. However, the existing methods…

Machine Learning · Computer Science 2024-05-30 Zhuang Qi , Junlin Zhang , Xiaming Chen , Xin Qi

It is well-known that real data often contain outliers. The term outlier typically refers to a case, that is, a row of the $n \times d$ data matrix. In recent times a different type has come into focus, the cellwise outliers. These are…

Methodology · Statistics 2024-07-08 Jakob Raymaekers , Peter J. Rousseeuw

The combination of the Internet of Things and the Edge Computing gives many opportunities to support innovative applications close to end users. Numerous devices present in both infrastructures can collect data upon which various processing…

Distributed, Parallel, and Cluster Computing · Computer Science 2021-03-02 Kostas Kolomvatsos , Christos Anagnostopoulos

Outlier detection is a well-researched and crucial problem in machine learning. However, there is little research on string data outlier detection, as most literature focuses on outlier detection of numerical data. A robust string data…

Machine Learning · Computer Science 2026-03-13 Philip Maus

We study the classic $k$-means/median clustering, which are fundamental problems in unsupervised learning, in the setting where data are partitioned across multiple sites, and where we are allowed to discard a small portion of the data by…

Distributed, Parallel, and Cluster Computing · Computer Science 2018-10-12 Jiecao Chen , Erfan Sadeqi Azer , Qin Zhang

The presence of outliers is prevalent in machine learning applications and may produce misleading results. In this paper a new method for dealing with outliers and anomal samples is proposed. To overcome the outlier issue, the proposed…

Machine Learning · Computer Science 2016-07-05 Parsa Bagherzadeh , Hadi Sadoghi Yazdi

The detection of outliers is of critical importance in the assurance of data quality. Outliers may exist in observed data or in data derived from these observed data, such as estimates and forecasts. An outlier may indicate a problem with…

Methodology · Statistics 2025-10-23 Charles D. Coleman , Thomas Bryan

The task of outlier detection is to find small groups of data objects that are exceptional when compared with rest large amount of data. Detection of such outliers is important for many applications such as fraud detection and customer…

Databases · Computer Science 2007-05-23 Zengyou He , Xiaofei Xu , Shengchun Deng

With predictive models becoming prevalent, companies are expanding the types of data they gather. As a result, the collected datasets consist not only of simple numerical features but also more complex objects such as time series, images,…

Machine Learning · Computer Science 2025-07-01 Sebastian Chwilczyński , Dariusz Brzezinski

A multivariate dataset consists of $n$ cases in $d$ dimensions, and is often stored in an $n$ by $d$ data matrix. It is well-known that real data may contain outliers. Depending on the situation, outliers may be (a) undesirable errors which…

Methodology · Statistics 2019-10-08 Peter J. Rousseeuw , Wannes Van den Bossche

There are a number of mathematical formalisms of the term "outlier" in statistics, though there is no consensus on what the right notion ought to be. Accordingly, we try to give a consistent and robust definition for a specific type of…

Methodology · Statistics 2022-07-27 Ahmet Zahid Balcıoğlu , Oğuz Gürerk

There exist multiple methods to detect outliers in multivariate data in the literature, but most of them require to estimate the covariance matrix. The higher the dimension, the more complex the estimation of the matrix becoming impossible…

Methodology · Statistics 2020-12-01 P. Navarro-Esteban , J. A. Cuesta-Albertos

The impact of outliers and anomalies on model estimation and data processing is of paramount importance, as evidenced by the extensive body of research spanning various fields over several decades: thousands of research papers have been…

Artificial Intelligence · Computer Science 2023-12-13 Madalina Olteanu , Fabrice Rossi , Florian Yger

High-dimensional data poses unique challenges in outlier detection process. Most of the existing algorithms fail to properly address the issues stemming from a large number of features. In particular, outlier detection algorithms perform…

Machine Learning · Computer Science 2020-09-22 Firuz Kamalov , Ho Hon Leung