How to get X Y coordinates of lattice graph using graph_tool

Question

I am creating a lattice graph using graph_tool. I am trying to create a Property Map that represents X Y coordinates in the graph. For instance, if I create a lattice graph with a height of 5 and a width of 10, I want the value of the property map for vertex 0 to be [0, 0], vertex 1 to be [1, 0], vertex 10 to be [0, 1], etc

I generated the image using the code below:

g = lattice([10, 5]) 
pos = sfdp_layout(graph)
graph_draw(graph, pos=pos, output_size=(500,500), vertex_text=graph.vertex_index, output="lattice.png")

In the code above the value of pos[0] is array([-16.4148811 , -11.80299953])

Am I in the right direction using sfdp_layout?

Answer 1

The vertices are numbered according to row-major ordering, so you can just compute the coordinates from their indices:

g = lattice([10, 5])                                                   
x = g.new_vp("double", arange(g.num_vertices()) % 10)                  
y = g.new_vp("double", arange(g.num_vertices()) // 10)                 
pos = group_vector_property([x,y])                                     

graph_draw(g, pos, output="lattice.png")