null_baum: Baum spin test null model

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

Baum spin test null model

Description

Spin-based null model with maximum-overlap parcel reassignment. After rotating vertex coordinates, each original parcel is assigned the value of the rotated parcel with the most vertex overlap.

Usage

null_baum(
  data,
  coords,
  parcellation,
  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).
parcellation	Integer vector of parcel labels for all vertices. 0 and NA indicate medial wall.
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

Baum GL et al. (2020) PNAS 117:21854-21861. doi:10.1073/pnas.2005518117

Examples

coords <- list(lh = matrix(rnorm(30), 10, 3), rh = matrix(rnorm(30), 10, 3))
parcellation <- c(rep(1L, 5), rep(2L, 5), rep(3L, 5), rep(4L, 5))
data <- c(1.0, 2.0, 3.0, 4.0)
nd <- null_baum(data, coords, parcellation, n_perm = 10L, seed = 1L)

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