\(\bar{\sigma}_i\) computing using raw accelerometry data

Sigma0 computes \(\bar{\sigma}_i\), which is needed for the Activity Index computing in computeActivityIndex

Sigma0(x, hertz = 30)

Arguments

x	A 4-column data frame containing the raw accelerometry data when the device is not worn. The 1st column has the record/index number. The 2nd to 4th columns contain the tri-axial raw acceleration. The data will be used to calculate \(\bar{\sigma}_i\).
hertz	The sample rate of the data.

Value

\(\bar{\sigma}_i\), a numeric vector of length one.

Examples

filename = system.file("extdata","sample_GT3X+.csv.gz",package="ActivityIndex")
res = ReadGT3XPlus(filename)
hertz = res$Hertz
x = res$Raw[ 1:1000, c("Time", "X", "Y", "Z")]
res = Sigma0(x, hertz = hertz)
testthat::expect_true(res ==  0.1843216371355338723)