ENMO is the vector magnitude of tri-axial acceleration minus one gravity,
with negative values truncated to zero (van Hees et al. 2013). For a
perfectly still sensor (magnitude 1 g) ENMO is 0; movement raises it. When an
epoch length is given, per-epoch mean ENMO is returned.
Usage
computeENMO(accel, sampling_rate = NULL, epoch_sec = NULL, unit = c("g", "mg"))
Arguments
- accel
An n x 3 matrix (or data frame) of acceleration in g units
(columns x, y, z).
- sampling_rate
Sampling rate in Hz (required if epoch_sec is set).
- epoch_sec
Epoch length in seconds for aggregation; NULL returns the
per-sample ENMO.
- unit
"g" (default) or "mg" (milli-g).
Value
A numeric vector of ENMO values (per sample, or per epoch).
References
van Hees VT, et al. (2013). PLoS ONE 8(4):e61691.
Examples
still <- matrix(rep(c(0, 0, 1), each = 100), ncol = 3)
max(computeENMO(still)) # ~ 0 for a static 1 g signal
#> [1] 0