Sedentary Breaks Detection

Description

This function identifies sedentary breaks in minute-to-minute accelerometer data.

Usage

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accel.sedbreaks(counts, weartime = NULL, thresh = 100, return.flags = FALSE, 
                skipchecks = FALSE)

Arguments

counts

Time series accelerometer counts vector.

weartime

Accelerometer wear time vector; must be same length as counts and consist of 1's and 0's (if specified).

thresh

Minimum count value that must be achieved to record a sedentary break.

return.flags

If TRUE, function returns vector of 0's and 1's in which 1's indicate minutes in which a sedentary break has occurred; if FALSE, function returns total number of sedentary breaks during monitoring period.

skipchecks

If TRUE, function skips error checking code and runs slightly faster.

Value

Either a single numeric value indicating the total number of sedentary breaks during the monitoring period, or a vector of same length as counts where 1's indicate minutes in which a sedentary break has occurred.

Note

If a wear time vector is not provided, algorithm may consider the first minute after a non-wear period as a sedentary break, which is not correct because the preceeding minute was non-wear time and may or may not have been sedentary time. This could result in a slight over-estimate of sedentary breaks.

Some additional information on the package accelerometry and its functions can be found on the author's website, https://sites.google.com/site/danevandomelen/

Author(s)

Dane R. Van Domelen

References

Acknowledgment: This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-0940903.

See Also

accel.weartime, accel.process.uni, accel.process.tri

Examples

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# Load in sample data frame
data(unidata)

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

# Identify periods of valid wear time
weartime.flag <- accel.weartime(counts = counts.part1)

# Count number of sedentary breaks (over full week)
num.sedbreaks <- accel.sedbreaks(counts = counts.part1, weartime = weartime.flag)

# Flag minutes that represent sedentary breaks
flag.sedbreaks <- accel.sedbreaks(counts = counts.part1, weartime = weartime.flag, 
                                  return.flags = TRUE)