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Lagged coherence between two signals

Source: R/coupling-spectral.R
laggedCoherence.Rd

Convenience wrapper for coherence with type = "lagged", the lagged (non-instantaneous) coherence of Pascual-Marqui (2007), Im(C) / sqrt(1 - Re(C)^2) where C is the complex coherency. Like the imaginary part of coherency it is insensitive to zero-lag / volume-conduction coupling.

Usage

laggedCoherence(
  x,
  y = NULL,
  sr = NULL,
  freq_range = NULL,
  nperseg = 256L,
  noverlap = NULL,
  method = c("welch", "multitaper"),
  modality_x = NULL,
  modality_y = NULL,
  channels_x = 1L,
  channels_y = 1L
)

Arguments

x

Numeric vector, PhysioExperiment, or MultiPhysioExperiment.

y

Numeric vector or PhysioExperiment, or NULL when x is an MPE.

sr

Numeric sampling rate in Hz (required when x/y are numeric).

freq_range

Numeric vector of length 2 giving the frequency range c(low, high) in Hz to restrict the output. NULL returns all frequencies.

nperseg

Integer segment length for Welch's method (default 256).

noverlap

Integer overlap between segments, or NULL for floor(nperseg / 2).

method

Character spectral estimation method. Currently only "welch" is implemented; "multitaper" is reserved for future use.

modality_x

Character modality name in MPE for the x signal.

modality_y

Character modality name in MPE for the y signal.

channels_x

Integer which channel to extract from x (default 1).

channels_y

Integer which channel to extract from y (default 1).

Value

A named list as returned by coherence, with type = "lagged".

References

Pascual-Marqui, R. D. (2007). Instantaneous and lagged measurements of linear and nonlinear dependence between groups of multivariate time series. arXiv:0711.1455.

See also

coherence

Examples

sr <- 200
t <- seq(0, 10, length.out = sr * 10)
x <- sin(2 * pi * 10 * t)
y <- sin(2 * pi * 10 * t + pi / 2)          # 90-degree lag
lc <- laggedCoherence(x, y, sr = sr, freq_range = c(8, 12))
max(abs(lc$coherence))
#> [1] 1