get_wear_flag {arctools}

Compute wear/non-wear flag

Description

Compute wear/non-wear flag (1/0) for each minute of activity counts data.

Usage

get_wear_flag(acc, nonwear_0s_minimum_window = 90)

Arguments

acc

A numeric vector. A minute-level activity counts data vector.

nonwear_0s_minimum_window

A numeric scalar. A minimum number of consecutive minutes with 0 activity count to be considered non-wear.

Details

Method implements wear/non-wear detection algorithm closely following that of Choi et al. (2011).

The wear/non-wear flag is determined based on activity counts data. A minute is classified as non-wear if it belongs to any nonwear_0s_minimum_window minutes-long interval of consecutive values 0 in activity counts data vector; here, "any interval" implies that a particular minute may be located at any location (beginning, middle, end) of interval of consecutive values 0 to be classified as a non-wear. Otherwise, a particular minute is classified as wear.

Similarly to recommendations in Discussion in Choi et al. (2011), the method assumes a threshold value of 0 for nonzero counts allowed during a nonwear time interval (I.e., no activity count equal >= 1 is allowed). The method also assumes 90 minutes as a default for minimum time of consecutive zero counts for a window to be flagged nonwear. Differently from recommendations in Discussion in Choi et al. (2011), it does not consider any "artifactual movement" interval of nonzero counts during a nonwear time interval.

Value

An integer vector. It has value 1 for a wear and 0 for non-wear flagged minute. It has the same vector length as acc vector. If there is an NA entry in acc vector, then the returned vector will have a corresponding entry set to NA too.

References

Choi, L., Liu, Z., Matthews, C. E., & Buchowski, M. S. (2011). Validation of accelerometer wear and nonwear time classification algorithm. Medicine and Science in Sports and Exercise. https://doi.org/10.1249/MSS.0b013e3181ed61a3

Examples

## Read exemplary data
fpath_i <- system.file("extdata", extdata_fnames[1], package = "arctools")
dat_i   <- as.data.frame(data.table::fread(fpath_i))
acc     <- dat_i$vectormagnitude
acc_ts  <- lubridate::ymd_hms(dat_i$timestamp)
## Get acc data vector in "midnight_to_midnight" format
acc <- midnight_to_midnight(acc, acc_ts)
## Get wear/non-wear flag
wear_flag <- get_wear_flag(acc)