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. 2011 Nov;17(9):705–711. doi: 10.1089/tmj.2011.0022

Fig. 2.

Fig. 2.

(a) The step-by-step procedures for motion-derived respiratory rate estimation, (b) raw 3D acceleration signals for 1 min episode, (c) the three vectors derived from 3D acceleration signals by using the band-pass filter based on 1-minute EE, and (d) the respiration wave derived from three vectors by using the PCA method. EE, energy expenditure; PCA, principal component analysis.