Hello,
I have just fitted an SBM to my graph. Having run state = gt.minimize_nested_blockmodel_dl(g, deg_corr=True) I now would like to investigate the results a bit more closely. More specifically I am after the best way to access all vertices assigned to a given block.
I can use get_levels() and then get_blocks() to obtain the block membership of each vertex and from that I can use find_vertex() for a given block number to find the list of all vertices in that block which I can then use to loop through them. I wonder, however, if there is a more efficient way of obtaining all vertices in a given block?
My current pseudo code looks something like the following:
state = gt.minimize_nested_blockmodel_dl(g, deg_corr=True) #now do something for all vertices in each of the blocks levels = state.get_levels() graphs = state.get_bstacks() #Return the nested levels as individual graphs. num_blocks = graphs[1].num_vertices() #find the number of blocks at level 0 blocks = levels[0].get_blocks() #Returns property map with block labels for each vertex. for i in range(num_blocks): #cycle through all blocks vs = gt.find_vertex(g,blocks,i) for v in vs: #cylce through all vertices in a given block do something
Is there some more efficient way of doing this that I am missing? I would ideally ultimately run it after each sweep of the mcmc algorithm so would like to minimise looping that I am doing in python if graph-tool has methods for what I am doing which will, presumably, be faster.
Thank you for any advice in advance!
With best wishes,
Philipp
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(I should probably add that I am only interested in relations between the nodes in a given block with each other, so am happy to work with vertex filters.)
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Ni! Hi Philipp,
Yes, there are more straightforward paths to the same information:
# get some graph and model it import graph_tool.all as gt g = gt.collection.data["celegansneural"] s = gt.minimize_nested_blockmodel_dl(g)
# get your groups of vertices in a dictionary l0 = s.levels[0] block2vertices = dict() for i in range(l0.B): block2vertices[i] = gt.find_vertex(l0.g, l0.b, i)
Cheers .~´
On Tue, Jun 19, 2018 at 7:01 PM, P-M pmj27@cam.ac.uk wrote:
(I should probably add that I am only interested in relations between the nodes in a given block with each other, so am happy to work with vertex filters.)
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Am 19.06.2018 um 21:01 schrieb Alexandre Hannud Abdo:
Ni! Hi Philipp,
Yes, there are more straightforward paths to the same information:
# get some graph and model it import graph_tool.all as gt g = gt.collection.data["celegansneural"] s = gt.minimize_nested_blockmodel_dl(g)
# get your groups of vertices in a dictionary l0 = s.levels[0] block2vertices = dict() for i in range(l0.B): block2vertices[i] = gt.find_vertex(l0.g, l0.b, i)
Since find_vertex() is O(N), the above is O(B * N). A faster O(N) approach is simply:
groups = defaultdict(list) for v in g.vertices(): groups[l0.b[v]].append(v)
Best, Tiago