type
This can be either NULL or 1 or 2. type = 1 means that the matrix contains 0, 1, 2, 3 where G[i, j] = g[j, i] = 0, means there is no edge between nodes i and j, G[i, j] = g[j, i] = 1, there is an edge between nodes i and j and G[i, j] = 2 and G[j, i] = 3 means that there is an arrow from node i to node j. If type 2, the matrix contains 0 for no edge and 1 for a directed edge. In this case, G[i,j]=1 and G[j,i]=0 means that there is an arrow from node i to node j. If you are not sure of what you have, just leave it NULL, the function will check to which case your matrix belongs.