Compute an HRF smoothing kernel — hrf_smoothing

This function computes a temporal similarity matrix from a series of hemodynamic response functions.

Usage

hrf_smoothing_kernel(
  len,
  TR = 2,
  form = onset ~ trialwise(),
  buffer_scans = 3L,
  normalise = TRUE,
  method = c("gram", "cosine")
)

len: The number of scans.
TR: The repetition time (default is 2 seconds).
form: the trialwise formula expression, see examples.
buffer_scans: The number of scans to buffer before and after the event.
normalise: Whether to normalise the kernel.
method: "gram" (inner products of the design rows) or "cosine" (the same, scaled to unit diagonal). With normalise = TRUE both give K[i, j] / sqrt(K[i, i] * K[j, j]), a symmetric matrix with unit diagonal.

a smoothing matrix

form <- onset ~ trialwise(basis="gaussian")
sk <- hrf_smoothing_kernel(100, TR=1.5, form)