Outlier detection by example

Cui Zhu, Hiroyuki Kitagawa, Spiros Papadimitriou, Christos Faloutsos

Research output: Contribution to journalArticle

7 Scopus citations


Outlier detection is a useful technique in such areas as fraud detection, financial analysis and health monitoring. Many recent approaches detect outliers according to reasonable, pre-defined concepts of an outlier (e.g., distance-based, density-based, etc.). However, the definition of an outlier differs between users or even datasets. This paper presents a solution to this problem by including input from the users. Our OBE (Outlier By Example) system is the first that allows users to provide examples of outliers in low-dimensional datasets. By incorporating a small number of such examples, OBE can successfully develop an algorithm by which to identify further outliers based on their outlierness. Several algorithmic challenges and engineering decisions must be addressed in building such a system. We describe the key design decisions and algorithms in this paper. In order to interact with users having different degrees of domain knowledge, we develop two detection schemes: OBE-Fraction and OBE-RF. Our experiments on both real and synthetic datasets demonstrate that OBE can discover values that a user would consider outliers.

Original languageEnglish (US)
Pages (from-to)217-247
Number of pages31
JournalJournal of Intelligent Information Systems
Issue number2
StatePublished - Apr 1 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Software
  • Information Systems
  • Hardware and Architecture
  • Computer Networks and Communications
  • Artificial Intelligence


  • Data mining
  • Machine learning
  • Outlier detection
  • Outlier example

Fingerprint Dive into the research topics of 'Outlier detection by example'. Together they form a unique fingerprint.

  • Cite this