Compute Parcel Adjacency Graph from an Atlas — atlas

Builds a region adjacency graph from a volumetric atlas. Two parcels are considered adjacent when at least one pair of their voxels are neighbours under the chosen connectivity scheme.

Usage

atlas_graph(
  atlas,
  connectivity = c("6", "18", "26"),
  as = c("matrix", "igraph", "tibble"),
  include_weight = TRUE
)

Arguments

atlas: An atlas object (must contain $atlas, $ids, and $labels).
connectivity: Character. Neighbourhood type: "6" (face), "18" (face + edge), or "26" (face + edge + corner). Default: "6".
as: Character. Output format: "matrix" (K x K adjacency matrix), "igraph" (igraph graph object), or "tibble" (edge-list data frame with from, to, weight columns). Default: "matrix".
include_weight: Logical. If TRUE (default), edge values are the count of shared boundary voxel pairs. If FALSE, edges are binary (0/1).

Value

Depending on as:

matrix: A symmetric integer matrix of dimension K x K with row/column names set to region labels.
igraph: An undirected igraph graph (requires the igraph package).
tibble: A data.frame (tibble if available) with columns from, to, and weight.

Examples

if (FALSE) { # \dontrun{
atlas <- get_schaefer_atlas(100)
adj   <- atlas_graph(atlas)
adj_b <- atlas_graph(atlas, include_weight = FALSE)
el    <- atlas_graph(atlas, as = "tibble")
} # }