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On-line detection of anomalies in time series is a key technique used in various event-sensitive scenarios such as robotic system monitoring, smart sensor networks and data center security. However, the increasing diversity of data sources…

Machine Learning · Computer Science 2021-04-26 Wentai Wu , Ligang He , Weiwei Lin , Yi Su , Yuhua Cui , Carsten Maple , Stephen Jarvis

Most of the existing methods for anomaly detection use only positive data to learn the data distribution, thus they usually need a pre-defined threshold at the detection stage to determine whether a test instance is an outlier.…

Machine Learning · Computer Science 2019-03-19 Kai Tian , Shuigeng Zhou , Jianping Fan , Jihong Guan

Anomaly detection in multivariate time series is an important problem across various fields such as healthcare, financial services, manufacturing or physics detector monitoring. Accurately identifying when unexpected errors or faults occur…

Machine Learning · Computer Science 2025-06-26 Laura Boggia , Rafael Teixeira de Lima , Bogdan Malaescu

Anomaly detection (AD), separating anomalies from normal data, has many applications across domains, from security to healthcare. While most previous works were shown to be effective for cases with fully or partially labeled data, that…

Machine Learning · Computer Science 2022-08-08 Jinsung Yoon , Kihyuk Sohn , Chun-Liang Li , Sercan O. Arik , Chen-Yu Lee , Tomas Pfister

Machine learning offers potential solutions to current issues in industrial systems in areas such as quality control and predictive maintenance, but also faces unique barriers in industrial applications. An ongoing challenge is extreme…

Machine Learning · Computer Science 2026-01-15 Lesley Wheat , Martin v. Mohrenschildt , Saeid Habibi

Time series anomaly detection is crucial for industrial monitoring services that handle a large volume of data, aiming to ensure reliability and optimize system performance. Existing methods often require extensive labeled resources and…

Machine Learning · Computer Science 2023-07-21 Manqing Dong , Zhanxiang Zhao , Yitong Geng , Wentao Li , Wei Wang , Huai Jiang

Organizations rely heavily on time series metrics to measure and model key aspects of operational and business performance. The ability to reliably detect issues with these metrics is imperative to identifying early indicators of major…

Machine Learning · Computer Science 2020-11-11 Sayan Chakraborty , Smit Shah , Kiumars Soltani , Anna Swigart , Luyao Yang , Kyle Buckingham

Change point detection is a crucial aspect of analyzing time series data, as the presence of a change point indicates an abrupt and significant change in the process generating the data. While many algorithms for the problem of change point…

Machine Learning · Computer Science 2023-05-23 Mario Krause

Detection of periodic patterns of interest within noisy time series data plays a critical role in various tasks, spanning from health monitoring to behavior analysis. Existing learning techniques often rely on labels or clean versions of…

Machine Learning · Computer Science 2025-06-24 Berken Utku Demirel , Christian Holz

Semi-supervised anomaly detection, which aims to improve the anomaly detection performance by using a small amount of labeled anomaly data in addition to unlabeled data, has attracted attention. Existing semi-supervised approaches assume…

Machine Learning · Statistics 2025-02-11 Hiroshi Takahashi , Tomoharu Iwata , Atsutoshi Kumagai , Yuuki Yamanaka

We study anomaly detection and introduce an algorithm that processes variable length, irregularly sampled sequences or sequences with missing values. Our algorithm is fully unsupervised, however, can be readily extended to supervised or…

Machine Learning · Statistics 2020-05-26 Oguzhan Karaahmetoglu , Fatih Ilhan , Ismail Balaban , Suleyman Serdar Kozat

Time-series anomaly detection deals with the problem of detecting anomalous timesteps by learning normality from the sequence of observations. However, the concept of normality evolves over time, leading to a "new normal problem", where the…

Machine Learning · Computer Science 2024-01-23 Dongmin Kim , Sunghyun Park , Jaegul Choo

Unsupervised outlier detection is attractive because it eliminates the need for labeled data. Moreover, forming multi-model ensembles can improve detection robustness. However, composing an ensemble without labeled data is challenging.…

Machine Learning · Computer Science 2026-05-19 Hong-Phuc Phan , Tuan-Anh Vu , Tung Kieu , Son Ha Xuan , Bin Yang , Christian S. Jensen

In various situations one is given only the predictions of multiple classifiers over a large unlabeled test data. This scenario raises the following questions: Without any labeled data and without any a-priori knowledge about the…

Machine Learning · Statistics 2014-10-31 Ariel Jaffe , Boaz Nadler , Yuval Kluger

Time-series anomaly detection, which detects errors and failures in a workflow, is one of the most important topics in real-world applications. The purpose of time-series anomaly detection is to reduce potential damages or losses. However,…

Machine Learning · Computer Science 2025-04-17 Jinsung Jeon , Jaehyeon Park , Sewon Park , Jeongwhan Choi , Minjung Kim , Noseong Park

Anomaly detection is a crucial task in various domains. Most of the existing methods assume the normal sample data clusters around a single central prototype while the real data may consist of multiple categories or subgroups. In addition,…

Machine Learning · Statistics 2024-12-03 Zhijin Dong , Hongzhi Liu , Boyuan Ren , Weimin Xiong , Zhonghai Wu

Obtaining labels for medical (image) data requires scarce and expensive experts. Moreover, due to ambiguous symptoms, single images rarely suffice to correctly diagnose a medical condition. Instead, it often requires to take additional…

Image and Video Processing · Electrical Eng. & Systems 2020-11-05 Diana Davletshina , Valentyn Melnychuk , Viet Tran , Hitansh Singla , Max Berrendorf , Evgeniy Faerman , Michael Fromm , Matthias Schubert

In semi-supervised learning, the prevailing understanding suggests that observing additional unlabeled samples improves estimation accuracy for linear parameters only in the case of model misspecification. In this work, we challenge such a…

Methodology · Statistics 2025-09-03 Kai Chen , Yuqian Zhang

Novelty detection is a critical task in various engineering fields. Numerous approaches to novelty detection rely on supervised or semi-supervised learning, which requires labelled datasets for training. However, acquiring labelled data,…

Machine Learning · Computer Science 2024-09-12 Ariel Priarone , Umberto Albertin , Carlo Cena , Mauro Martini , Marcello Chiaberge

Due to the unsupervised nature of anomaly detection, the key to fueling deep models is finding supervisory signals. Different from current reconstruction-guided generative models and transformation-based contrastive models, we devise novel…

Machine Learning · Computer Science 2023-05-26 Hongzuo Xu , Yijie Wang , Juhui Wei , Songlei Jian , Yizhou Li , Ning Liu