Approximation of the Optimal ROC Curve and a Tree-Based Ranking Algorithm

  • Authors:
  • Stéphan Clémençon;Nicolas Vayatis

  • Affiliations:
  • LTCI, Telecom Paristech (TSI), UMR Institut Telecom/CNRS 5141,;CMLA, ENS Cachan & UniverSud - UMR CNRS 8536, Cachan cedex, France 94235

  • Venue:
  • ALT '08 Proceedings of the 19th international conference on Algorithmic Learning Theory
  • Year:
  • 2008

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Abstract

We consider the extension of standard decision tree methods to the bipartite rankingproblem. In ranking, the goal pursued is global: define an order on the whole input space in order to have positive instances on top with maximum probability. The most natural way of ordering all instances consists in projecting the input data xonto the real line using a real-valued scoring functionsand the accuracy of the ordering induced by a candidate sis classically measured in terms of the AUC. In the paper, we discuss the design of tree-structured scoring functions obtained by maximizing the AUC criterion. In particular, the connection with recursive piecewise linear approximation of the optimal ROC curve both in the L1-sense and in the L茂戮驴-sense is discussed.