Optimal expectile smoothing

  • Authors:
  • Sabine K. Schnabel;Paul H. C. Eilers

  • Affiliations:
  • Max Planck Institute for Demographic Research, Rostock, Germany;Department of Biostatistics, Erasmus Medical Center, Rotterdam, The Netherlands

  • Venue:
  • Computational Statistics & Data Analysis
  • Year:
  • 2009

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Abstract

Quantiles are computed by optimizing an asymmetrically weighted L"1 norm, i.e. the sum of absolute values of residuals. Expectiles are obtained in a similar way when using an L"2 norm, i.e. the sum of squares. Computation is extremely simple: weighted regression leads to the global minimum in a handful of iterations. Least asymmetrically weighted squares are combined with P-splines to compute smooth expectile curves. Asymmetric cross-validation and the Schall algorithm for mixed models allow efficient optimization of the smoothing parameter. Performance is illustrated on simulated and empirical data.