Activity Counts from a Raw Axivity .cwa File

Reads a raw Axivity (.cwa) accelerometer file and converts it to ActiGraph-equivalent activity counts via the agcounts implementation of the ActiGraph count algorithm (Neishabouri 2022). Requires the GGIRread and agcounts packages.

Usage

axivity.counts(path, epoch = 60, lfe = FALSE, tz = "UTC")

Arguments

path

Path to a .cwa file.

epoch

Epoch length in seconds (default 60).

lfe

Use the low-frequency extension filter (default FALSE).

tz

Time zone for the timestamps (default "UTC").

Value

Data frame with time, axis1, axis2, axis3 and vm, one row per epoch (the same shape as gt3x.counts).

Cross-brand counts

These are an approximation of ActiGraph counts, not native ActiGraph output. Axivity-to-count conversion has been directly validated (Brond et al. 2017). The result is appropriate for the relative and normalized circadian metrics in this package (IS, IV, RA, L5, M10, SRI); it should not be used to apply ActiGraph intensity cut-points or to compare absolute counts across device brands.

References

Neishabouri A, Nguyen J, Samuelsson J, Guthrie T, Biggs M, Wyatt J, Cross D, Karas M, Migueles JH, Khan S, Guo CC (2022). “Quantification of acceleration as activity counts in ActiGraph wearable.” Scientific Reports, 12, 11958. doi:10.1038/s41598-022-16003-x .

Brond JC, Andersen LB, Arvidsson D (2017). “Generating ActiGraph counts from raw acceleration recorded by an alternative monitor.” Medicine & Science in Sports & Exercise, 49(11), 2351–2360. doi:10.1249/MSS.0000000000001344 .

See also

geneactiv.counts, gt3x.counts, read.raw