Create 3D Blocks for Voxelwise Analysis — create_3d

Creates spatial blocks from a 3D mask for use with spatial_fdr. This is useful for voxelwise analyses where you want to group nearby voxels together for more powerful multiple comparisons correction.

Usage

create_3d_blocks(mask, block_size = c(10, 10, 10), connectivity = 26)

Arguments

mask: Numeric 3D array or NeuroVol object defining the brain mask. Non-zero values indicate voxels to include.
block_size: Integer vector of length 3 specifying block dimensions in voxels (default: c(10, 10, 10))
connectivity: Integer scalar; type of connectivity for neighbors: 6 (face connectivity) or 26 (face, edge, and corner connectivity). Default: 26

Value

List with components:

group_id: Integer vector of group IDs for each voxel in the mask
neighbors: List of length n_groups where element i contains integer vector of 1-based neighbor IDs for group i
n_groups: Integer scalar; total number of groups created
block_size: Block size used

Examples

mask <- array(c(1L, 1L, 0L,
                1L, 1L, 0L,
                0L, 0L, 0L), dim = c(3, 3, 1))
blocks <- create_3d_blocks(mask, block_size = c(2, 2, 1))
blocks$n_groups
#> [1] 1