null_alexander_bloch: Alexander-Bloch spin test null model

In neuromapr: Spatial Null Models and Transforms for Brain Map Comparison

Alexander-Bloch spin test null model

Description

Original vertex-level spin test: rotates coordinates and assigns each rotated vertex the value of its nearest original vertex (no optimal matching).

Usage

null_alexander_bloch(
  data,
  coords,
  n_perm = 1000L,
  seed = NULL,
  rotation = c("euler", "rodrigues")
)

Arguments

data	Numeric vector of brain map values.
coords	List with ⁠$lh⁠ and ⁠$rh⁠ matrices of spherical coordinates (n x 3 each).
n_perm	Integer number of null permutations to generate.
seed	Optional integer seed for reproducibility.
rotation	Rotation generation method: "euler" (ZYZ Euler angles, default, matches neuromaps Python) or "rodrigues" (Rodrigues axis-angle formula).

Value

A null_distribution object.

References

Alexander-Bloch AF et al. (2018) NeuroImage 175:111-120. doi:10.1016/j.neuroimage.2018.04.023

Examples

coords <- list(lh = matrix(rnorm(30), 10, 3), rh = matrix(rnorm(30), 10, 3))
data <- rnorm(20)
nd <- null_alexander_bloch(data, coords, n_perm = 10L, seed = 1L)

neuromapr documentation built on Feb. 27, 2026, 5:08 p.m.