Assemble a physiological node matrix — physioNodeMatrix • PhysioNetPhysiology

Builds the time-by-nodes matrix that timeDelayStability() consumes, where each node is one physiological variable (an organ system or a derived feature such as an EEG band-power, heart rate, respiration amplitude, or an EMG envelope). Inputs are a named list of equal-length numeric vectors, a numeric matrix, or a data frame.

Usage

physioNodeMatrix(
  x,
  nodes = NULL,
  standardize = FALSE,
  assay = NULL,
  channels = NULL,
  feature = c("raw", "envelope"),
  target_rate = NULL
)

Arguments

x: A named list of equal-length numeric vectors, a numeric matrix (time x nodes), a data frame of numeric columns, or a PhysioExperiment / MultiPhysioExperiment object (channels/modalities become nodes).
nodes: Optional character vector of node names (defaults to the names of x).
standardize: If TRUE, z-normalise each column (default FALSE; TDS z-normalises per window internally, so this is usually unnecessary).
assay: For a PhysioExperiment, which assay to read (default: its default assay).
channels: For a PhysioExperiment, an optional subset of channels.
feature: Per-channel feature: "raw" (default) or "envelope" (the analytic-signal amplitude — often the right node series for coupling).
target_rate: Optional rate (Hz) to down-sample each channel to, by block-averaging. Required for a MultiPhysioExperiment whose experiments have differing sampling rates.

Value

A numeric matrix, time (rows) by nodes (columns), with column names.

Details

In Network Physiology, coupling is assessed between the dynamics of these variables, so nodes are typically instantaneous features sampled on a common, relatively slow grid (e.g. 1 Hz), not the raw high-rate waveforms. Assemble such features with the relevant Physio* package and pass them here.

Examples

nodes <- list(
  hr   = cumsum(rnorm(500)),
  resp = sin(seq(0, 20 * pi, length.out = 500)),
  emg  = abs(rnorm(500))
)
M <- physioNodeMatrix(nodes)
dim(M)
#> [1] 500   3