alffmap — alffmap • ANTsR

Amplitude of Low Frequency Fluctuations (ALFF; Zang et al., 2007) and fractional Amplitude of Low Frequency Fluctuations (f/ALFF; Zou et al., 2008) are related measures that quantify the amplitude of low frequency oscillations (LFOs). This function outputs ALFF and fALFF for the input.

alffmap(
  x,
  flo = 0.01,
  fhi = 0.1,
  tr = 1,
  detrend = TRUE,
  takesqrt = FALSE,
  kernel
)

Arguments

x: input vector for the time series of interest
flo: low frequency, typically 0.01
fhi: high frequency, typically 0.1
tr: the period associated with the vector x (inverse of frequency)
detrend: detrend the input time series
takesqrt: take the sqrt of the computed values
kernel: smoothing kernel in estimate, see spec.pgram

Value

vector is output showing ALFF and fALFF values

Author

Avants BB

Examples



set.seed(1)
mat <- matrix(rnorm(3000), ncol = 50)
fallf <- apply(mat, FUN = alffmap, MARGIN = 2)
k <- kernel("daniell", rep(2, 3))
fallf2 <- apply(mat, FUN = alffmap, MARGIN = 2, kernel = k)
testthat::expect_equal(mean(fallf2), 3.00367017972746)