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Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
In this thesis we develop methods for classifying physical activity using accelerometer recordings. We cast this as a problem of classification in time series with moderate to high dimensional observations at each time point. Specifically, we observe a vector of summary statistics of the accelerometer signal at each point in time, and we wish to use these observations to estimate the type and intensity of physical activity the individual engaged in as it changes over time.
Our methods are based on Conditional Random Fields, which allow us to capture temporal dependence in an individual’s physical activity type without requiring us to model the distribution of the observed features at each point in time. We develop three novel estimation strategies for Conditional Random Fields, evaluate their performance on classification tasks through simulation studies and demonstrate their use in applications with real physical activity data sets.
Ray, Evan L., "Physical Activity Classification with Conditional Random Fields" (2015). Doctoral Dissertations. 427.