Partial Directed Coherence for multichannel / multimodal signals

Frequency-resolved directed connectivity via Partial Directed Coherence (Baccala & Sameshima 2001), computed from the coefficient matrix of an MVAR model (PhysioCore::mvarFit()); numerically identical to PhysioEEG's eegPDC. Unlike DTF, PDC reflects only direct influences, so a purely indirect pathway gives PDC near zero.

Usage

partialDirectedCoherence(
  x,
  y = NULL,
  sr = NULL,
  order = 5L,
  freqs = NULL,
  generalized = TRUE,
  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).

generalized

Use generalized PDC (inverse-noise weighting; default TRUE).

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 as in directedTransferFunction() with a pdc array and band-averaged matrix; for a two-channel input, pdc_xy and pdc_yx.

References

Baccala, L. A., & Sameshima, K. (2001). Partial directed coherence: a new concept in neural structure determination. Biological Cybernetics, 84(6), 463-474.

See also

directedTransferFunction(), transferEntropy()

Examples

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