Department of Mathematics
 Search | Help | Login | pdf version | printable version

Math @ Duke



Publications [#212344] of Ezra Miller

Papers Submitted

  1. with Megan Owen and Scott Provan, Polyhedral computational geometry for averaging metric phylogenetic trees (2012) (43 pages.) [math.MG/1211.7046]
    (last updated on 2013/12/20)

    This paper investigates the computational geometry relevant to calculations of the Fréchet mean and variance for probability distributions on the phylogenetic tree space of Billera, Holmes and Vogtmann, using the theory of probability measures on spaces of nonpositive curvature developed by Sturm. We show that the combinatorics of geodesics with a specified fixed endpoint in tree space are determined by the location of the varying endpoint in a certain polyhedral subdivision of tree space. The variance function associated to a finite subset of tree space is continuously differentiable within each cell of the corresponding subdivision. We use this subdivision to establish two iterative methods for producing sequences that converge to the Fréchet mean: one based on Sturm's Law of Large Numbers, and another based on descent algorithms for finding optima of smooth functions on convex polyhedra. We present properties and biological applications of Frechet means and extend our main results to more general globally nonpositively curved spaces composed of Euclidean orthants.
ph: 919.660.2800
fax: 919.660.2821

Mathematics Department
Duke University, Box 90320
Durham, NC 27708-0320