Robust estimation of location and scatter by pruning the minimum spanning tree

  • Authors:
  • Thomas Kirschstein;Steffen Liebscher;Claudia Becker

  • Affiliations:
  • -;-;-

  • Venue:
  • Journal of Multivariate Analysis
  • Year:
  • 2013

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Abstract

One of the most essential topics in robust statistics is the robust estimation of location and covariance. Many popular robust (location and scatter) estimators such as Fast-MCD, MVE, and MZE require at least a convex distribution of the underlying data. In the case of non-convex data distributions these approaches may lead to a suboptimal result caused by the application of Mahalanobis distances with respect to location and covariance of a suitably chosen subsample of the data-implying a convex structure. The approach presented here fixes this drawback using Euclidean distances. The data set is treated as a complete network and the minimum spanning tree (MST) for this data set is calculated. Based on the MST a subset of relevant points (thought of as an ''outlier-free'' subsample of minimum size) is determined which can then be used for calculating data characteristics. It is shown, that the approach has a maximum breakdown point. Additionally, a simulation study provides insights in the approach's behaviour with respect to increasing dimension and size.