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Directed Transfer Function for multichannel / multimodal signals

Source: R/coupling-directed.R
directedTransferFunction.Rd

Frequency-resolved directed connectivity via the Directed Transfer Function (Kaminski & Blinowska 1991), computed from the transfer function of a multivariate autoregressive model fitted with PhysioCore::mvarFit(). This cross-modal implementation is numerically identical to PhysioEEG's eegDTF on the same input. Because the transfer function inverts the whole VAR system, DTF reflects both direct and indirect pathways.

Usage

directedTransferFunction(
  x,
  y = NULL,
  sr = NULL,
  order = 5L,
  freqs = NULL,
  normalized = TRUE,
  ffDTF = FALSE,
  band = NULL,
  mvar_method = "ols",
  modality_x = NULL,
  modality_y = NULL,
  channels_x = NULL,
  channels_y = NULL
)

Arguments

x

A multichannel matrix (time x channels) or PhysioExperiment (with y = NULL), or one signal / PhysioExperiment of a pair.

y

The second signal / PhysioExperiment of a pair, or NULL for a single multichannel input.

sr

Sampling rate in Hz (required for numeric-matrix input).

order

MVAR model order (default: 5), or NULL to select automatically.

freqs

Frequencies in Hz (default: 128 points from 0 to the Nyquist frequency).

normalized

Row-normalize the DTF (default: TRUE).

ffDTF

Use the full-frequency DTF normalization (default: FALSE).

band

Optional length-2 band in Hz over which to average the returned matrix (default: all frequencies).

mvar_method

MVAR estimator (default: "ols").

modality_x, modality_y, channels_x, channels_y

Passed to the shared signal-pair extraction when y is supplied.

Value

A list with dtf (n x n x n_freqs array), the band-averaged directed matrix (rows = targets, columns = sources), frequencies, channels, and order. For a two-channel input, dtf_xy and dtf_yx give the directional summaries.

References

Kaminski, M. J., & Blinowska, K. J. (1991). A new method of the description of the information flow in the brain structures. Biological Cybernetics, 65(3), 203-210.

See also

partialDirectedCoherence(), transferEntropy(), grangerCausality()

Examples

set.seed(1)
X <- matrix(rnorm(1500), ncol = 3)
res <- directedTransferFunction(X, sr = 100, order = 4)
dim(res$dtf)
#> [1]   3   3 128