Curve Registration of Daily Activity Profiles

Aligns each day's 24-hour activity profile on its active-phase landmark (the M10 centre), separating the horizontal phase variation (how the timing shifts day to day) from the vertical amplitude variation (the registered mean profile, sharper than the plain average because phase jitter no longer blurs it). The per-day landmark times are a scale-invariant phase marker (the M10-window centre), unchanged by any rescaling of the counts (Ramsay and Silverman 2005).

Usage

curve.registration(counts, timestamps, n_grid = 144L, period = 24)

Arguments

counts

Numeric activity vector.

timestamps

POSIXct timestamps, one per value.

n_grid

Bins per day for the profile (default 144 = 10-minute bins).

period

Period in hours (default 24).

Value

An object of class actiRhythm_registration: a per-day landmark table (L5 and M10 centre hours), the circular-mean landmarks, the phase variability (circular SD of the M10 landmark), and the registered mean profile. Never errors.

References

Ramsay JO, Silverman BW (2005). Functional Data Analysis, 2nd edition. Springer. doi:10.1007/b98888 .

Van Someren EJW, Swaab DF, Colenda CC, Cohen W, McCall WV, Rosenquist PB (1999). “Bright light therapy: improved sensitivity to its effects on rest-activity rhythms in Alzheimer patients by application of nonparametric methods.” Chronobiology International, 16(4), 505–518. doi:10.3109/07420529908998724 .

Examples

ts <- seq(as.POSIXct("2024-01-01", tz = "UTC"), by = 60, length.out = 5 * 1440)
h  <- as.numeric(format(ts, "%H"))
curve.registration(ifelse(h >= 23 | h < 7, 5, 300), ts)
#> Curve Registration (landmark)
#> 
#>   Days registered:   5
#>   Mean L5 centre:    02.50 h
#>   Mean M10 centre:   12.00 h
#>   Phase variability: -0.00 h (circular SD of M10)
#>