Robust kernel density estimation

  • Authors:
  • JooSeuk Kim;Clayton D. Scott

  • Affiliations:
  • Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI;Department of Statistics and Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI

  • Venue:
  • The Journal of Machine Learning Research
  • Year:
  • 2012

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Abstract

We propose a method for nonparametric density estimation that exhibits robustness to contamination of the training sample. This method achieves robustness by combining a traditional kernel density estimator (KDE) with ideas from classical M-estimation. We interpret the KDE based on a positive semi-definite kernel as a sample mean in the associated reproducing kernel Hilbert space. Since the sample mean is sensitive to outliers, we estimate it robustly via M-estimation, yielding a robust kernel density estimator (RKDE). An RKDE can be computed efficiently via a kernelized iteratively re-weighted least squares (IRWLS) algorithm. Necessary and sufficient conditions are given for kernelized IRWLS to converge to the global minimizer of the M-estimator objective function. The robustness of the RKDE is demonstrated with a representer theorem, the influence function, and experimental results for density estimation and anomaly detection.