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Activity Number: 635 - Monitoring Health Behaviors with Multi-Sensor Mobile Technology
Type: Invited
Date/Time: Thursday, August 1, 2019 : 10:30 AM to 12:20 PM
Sponsor: ENAR
Abstract #300607 Presentation
Title: Registration for Exponential Family Functional Data
Author(s): Julia Wrobel and Vadim Zipunnikov and Jennifer Schrack and Jeff Goldsmith*
Companies: Columbia University and Johns Hopkins University and Johns Hopkins University and Columbia University
Keywords: Functional data; Smoothing; Computation

We introduce a novel method for separating amplitude and phase variability in exponential family functional data. Our method alternates between two steps: the first uses generalized functional principal components analysis (GFPCA) to calculate template functions, and the second estimates smooth warping functions that map observed curves to templates. Existing approaches to registration have primarily focused on continuous functional observations, and the few approaches for discrete functional data require a pre-smoothing step; these methods are frequently computationally intensive. In contrast, we focus on the likelihood of the observed data and avoid the need for preprocessing, and we implement both steps of our algorithm in a computationally efficient way. Our motivation comes from the Baltimore Longitudinal Study on Aging, in which accelerometer data provides valuable insights into the timing of sedentary behavior. We analyze binary functional data with observations each minute over 24 hours for 592 participants, where values represent activity and inactivity.

Authors who are presenting talks have a * after their name.

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