Detect non-wear periods — detectNonWear • PhysioWearable

Flags non-wear windows where the accelerometer is stationary: at least min_axes of the three axes have a low standard deviation and value range over a long window (van Hees et al. 2011).

Usage

detectNonWear(
  accel,
  sampling_rate,
  window_min = 60,
  step_min = NULL,
  sd_thresh = 0.013,
  range_thresh = 0.05,
  min_axes = 2L
)

Arguments

accel: An n x 3 matrix of acceleration in g units.
sampling_rate: Sampling rate in Hz.
window_min: Window length in minutes (default 60).
step_min: Window step in minutes; NULL uses window_min / 4. A sliding (overlapping) window prevents a non-wear period from being diluted across a block boundary.
sd_thresh: Per-axis standard-deviation threshold (default 0.013 g).
range_thresh: Per-axis value-range threshold (default 0.050 g).
min_axes: Number of axes that must meet both criteria (default 2).

Value

A nonwear list with a per-window windows data frame (window, start_time, end_time, nonwear) and the nonwear_fraction (fraction of samples covered by any non-wear window).

References

van Hees VT, et al. (2011). PLoS ONE 6(7):e22922.