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Ranking and empirical minimization of U-statistics

arXiv (Cornell University)Published 5 March 2006Open access
Stéphan Clémençon, Gábor Lugosi, Nicolas Vayatis
Citations155
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Abstract

The problem of ranking/ordering instances, instead of simply classifying\nthem, has recently gained much attention in machine learning. In this paper we\nformulate the ranking problem in a rigorous statistical framework. The goal is\nto learn a ranking rule for deciding, among two instances, which one is\n"better," with minimum ranking risk. Since the natural estimates of the risk\nare of the form of a U-statistic, results of the theory of U-processes are\nrequired for investigating the consistency of empirical risk minimizers. We\nestablish in particular a tail inequality for degenerate U-processes, and apply\nit for showing that fast rates of convergence may be achieved under specific\nnoise assumptions, just like in classification. Convex risk minimization\nmethods are also studied.\n

Keywords

Computer Science