[igraph] Suspicious results produced by the function neighborhood

Hi all!

I came across some suspicious results by the igraph function neighborhood_size:

neighborhood_size(vertices=None, order=1, mode=ALL)

For each vertex specified by vertices, this function should return the number of vertices reachable from that vertex in at most order steps. My network is a directed citation network containing 531, 480 vertices (each is a paper) and their citation relationships (about 6 million edges). I used neighborhood_size to calculate the number of vertices reachable from a vertex in at most 50 steps and it returned a result of 506, 255. I am quite sure there couldn't be so many vertices reachable from that vertex. So I used Networkx to calculate the same thing and it returned a result of 17, 564, which seems to be more reasonable.

All the output about my current research is based on igraph. But I found so many suspicious results of this kind. Can anyone help me find out what the problem is?

Thanks!

Chao

Chao MIN, 闵超
Visiting PhD student, School of Informatics and Computing, Indiana University Bloomington
PhD candidate, School of Information Management, Nanjing University

From:	闵超
Subject:	[igraph] Suspicious results produced by the function neighborhood_size
Date:	Sat, 10 Jun 2017 15:40:18 -0400

[igraph] Suspicious results produced by the function neighborhood_size