The brain connectome is represented by a connectivity matrix. The adjacency matrix is represented differently according to the type of Graph. An adjacency matrix is square, and its elements indicate whether the pairs of vertices are connected or related. As a convention, its diagonal elements are set to 0, as a node is not connected to itself.
A Graph can have different characteristics. To name some, a Graph can be weighted or binary, directed or undirected, and unilayer or multilayer. A visual representation of the representation of unilayer Graphs in BRAPH 2 is shown below:
A unilayer graph is represented by nodes connected with edges. This type of graph is used for single-layer weighted analysis (WU, WD).
Multiple unconnected layers of graphs make a multigraph. A multigraph is used for single-layer density (BUD) and threshold (BUT) analyses.