ranking vertices by value of vertex property

graph-tool
1

Hi,
I ran PageRank on my graph, and now I need to get the top-k highest scored.
Is there any faster / more straightforward way of achieving this than by
creating and then sorting a new dictionary, as in the following method?

def top_k_page_rank(g, pagerank_prop, k):
    pr_sorted_scores = sort_pagerank_scores(g, pagerank_prop)
    top_k = list(pr_sorted_scores.items())[0:k]
    return top_k

def sort_pagerank_scores(g, pagerank_prop):
    pr_scores = dict()
    for v in g.vertices():
        pr_scores[v] = g.vertex_properties[pagerank_prop][v]
    pr_sorted_scores = {k: v for k, v in sorted(pr_scores.items(),
key=lambda item: item[1], reverse=True)}
    return pr_sorted_scores

Thanks,
Ioana

2

Yes, you can access property map values as numpy arrays via the ".a"
attribute, e.g. if pr is a vertex property map with the pagerank scores,
then

   pr.a

will give you a numpy array. This means you can use the argsort() method
to obtain the indexes (i.e. vertices) in increasing order:

   pr.a.argsort()

Best,
Tiago

3

Great, thanks a lot!
-Ioana

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