Computes the weighted Phase Lag Index between two signals. wPLI weights each phase-difference sample by the magnitude of the imaginary component of the cross-spectrum, reducing the influence of noise sources that produce phase differences near 0 or pi.
Usage
weightedPLI(
x,
y = NULL,
sr = NULL,
freq_band,
debiased = TRUE,
modality_x = NULL,
modality_y = NULL,
channels_x = 1L,
channels_y = 1L
)Arguments
- x
Numeric vector, PhysioExperiment, or MultiPhysioExperiment.
- y
Numeric vector or PhysioExperiment (NULL when
xis an MPE).- sr
Numeric sampling rate in Hz (required when x/y are numeric).
- freq_band
Numeric vector of length 2 specifying the frequency band
c(low, high)in Hz. Required.- debiased
Logical; if TRUE (default), also compute the debiased wPLI estimator.
- modality_x
Character modality name in MPE for x signal.
- modality_y
Character modality name in MPE for y signal.
- channels_x
Integer channel index to extract from x (default 1).
- channels_y
Integer channel index to extract from y (default 1).
Value
A named list with components:
- wpli
Numeric scalar in [0, 1] – the weighted PLI.
- wpli_debiased
Numeric scalar – the debiased wPLI, or NULL if
debiased = FALSE.- n_samples
Integer – number of time-domain samples used.
Details
$$\text{wPLI} = \frac{\left|\sum |\text{Im}(S_{xy})| \cdot \text{sign}(\text{Im}(S_{xy}))\right|}{\sum |\text{Im}(S_{xy})|}$$
When debiased = TRUE, the debiased estimator from Vinck et al. (2011) is
also returned:
$$\text{wPLI}_{\text{debiased}} = \frac{(\sum \text{Im}(S_{xy}))^2 - \sum \text{Im}(S_{xy})^2}{(\sum |\text{Im}(S_{xy})|)^2 - \sum \text{Im}(S_{xy})^2}$$
References
Vinck, M., Oostenveld, R., van Wingerden, M., Battaglia, F., & Pennartz, C. M. A. (2011). An improved index of phase-synchronization for electrophysiological data in the presence of volume-conduction, noise and sample-size bias. NeuroImage, 55(4), 1548–1565.
Lachaux, J.-P., Rodriguez, E., Martinerie, J., & Varela, F. J. (1999). Measuring phase synchrony in brain signals. Human Brain Mapping, 8(4), 194–208.