intensities {accelerometry}

Physical Activity Intensities

Description

Given a vector of accelerometer count values, calculates time spent in 5 mutually exclusive user-defined intensity levels (typically representing sedentary, light, lifestyle, moderate, and vigorous) as well as the total counts accumulated in various intensities. Non-wear time should be removed from counts before calling intensities to avoid overestimating sedentary time.

Usage

intensities(counts, int_cuts = as.integer(c(100, 760, 2020, 5999)))

Arguments

counts

Integer vector with accelerometer count values.

int_cuts

Numeric vector with four cutpoints from which five intensity ranges are derived. For example, int_cuts = c(100, 760, 2020, 5999) creates: 0-99 = intensity 1; 100-759 = intensity level 2; 760-2019 = intensity 3; 2020-5998 = intensity 4; >= 5999 = intensity 5.

Value

Integer vector of length 16 in which the first eight values are minutes in intensities 1, 2, 3, 4, 5, 2-3, 4-5, and 2-5, and the next eight are counts accumulated during time spent in each of those intensities.

Examples

# Load accelerometer data for first 5 participants in NHANES 2003-2004
data(unidata)

# Get data from ID number 21005
counts.part1 <- unidata[unidata[, "seqn"] == 21005, "paxinten"]

# Create vector of counts during valid wear time only
counts.part1.wear <- counts.part1[weartime(counts = counts.part1) == 1]

# Calculate physical activity intensity variables
intensity.variables <- intensities(counts = counts.part1.wear)