How to get close to the median shape

  • Authors:
  • Sariel Har-Peled

  • Affiliations:
  • Department of Computer Science, University of Illinois, Urbana, IL

  • Venue:
  • Computational Geometry: Theory and Applications - Special issue on the 21st European workshop on computational geometry (EWCG 2005)
  • Year:
  • 2007

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Abstract

In this paper, we study the problem of L1-fitting a shape to a set of n points in Rd (where d is a fixed constant), where the target is to minimize the sum of distances of the points to the shape, or alternatively the sum of squared distances. We present a general technique for computing a (1 + ε)-approximation for such a problem, with running time O(n + poly(logn, 1/ε)), where poly(logn, 1/ε) is a polynomial of constant degree of logn and 1/ε (the power of the polynomial is a function of d). This is a linear time algorithm for a fixed ε 0, and is the first subquadratic algorithm for this problem. Applications of the algorithm include best fitting either a circle, a sphere or a cylinder to a set of points when minimizing the sum of distances (or squared distances) to the respective shape.