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Title: Segmenting accelerometer data from daily life with unsupervised machine learning
Authors: van Kuppevelt, Dafne E.
Heywood, Joe
Hamer, Mark
Sabia, Severine
Fitzsimons, Emla
van Hees, Vincent T.
Issue Date: 2019
Publisher: Public Library of Science (PLoS) © van Kuppevelt et al.
Citation: VAN KUPPEVELT, D.E. ... et al, 2019. Segmenting accelerometer data from daily life with unsupervised machine learning. PLoS ONE, 14 (1), e0208692.
Abstract: Purpose: Accelerometers are increasingly used to obtain valuable descriptors of physical activity for health research. The cut-points approach to segment accelerometer data is widely used in physical activity research but requires resource expensive calibration studies and does not make it easy to explore the information that can be gained for a variety of raw data metrics. To address these limitations, we present a data-driven approach for segmenting and clustering the accelerometer data using unsupervised machine learning. Methods: The data used came from five hundred fourteen-year-old participants from the Millennium cohort study who wore an accelerometer (GENEActiv) on their wrist on one weekday and one weekend day. A Hidden Semi-Markov Model (HSMM), configured to identify a maximum of ten behavioral states from five second averaged acceleration with and without addition of x, y, and z-angles, was used for segmenting and clustering of the data. A cut-points approach was used as comparison. Results: Time spent in behavioral states with or without angle metrics constituted eight and five principal components to reach 95% explained variance, respectively; in comparison four components were identified with the cut-points approach. In the HSMM with acceleration and angle as input, the distributions for acceleration in the states showed similar groupings as the cut-points categories, while more variety was seen in the distribution of angles. Conclusion: Our unsupervised classification approach learns a construct of human behavior based on the data it observes, without the need for resource expensive calibration studies, has the ability to combine multiple data metrics, and offers a higher dimensional description of physical behavior. States are interpretable from the distributions of observations and by their duration.
Description: This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/
Version: Published
DOI: 10.1371/journal.pone.0208692
URI: https://dspace.lboro.ac.uk/2134/36287
Publisher Link: https://doi.org/10.1371/journal.pone.0208692
Appears in Collections:Published Articles (Sport, Exercise and Health Sciences)

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