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)