
From:  Tamas Nepusz 
Subject:  Re: [igraph] how to compare two networks... 
Date:  Sat, 19 Apr 2008 00:53:05 +0200 
Dear Simone,I think the difference lies between how igraph and sna handles multiple edges. Both of your networks have multiple edges. sna collapses multiple edges into one single edge and then takes the symmetric difference of the two edge sets  at least that is what I assume, since I obtained the same result in Python after doing these operations manually on your networks (hdist = 611). Strictly speaking, this method is incorrect if there are multiple edges and they have to be taken into account. In this sense, the approach described by Gabor is better: get the adjacency matrices, take the difference of the two matrices, take the absolute value of every element in the difference matrix and then sum the elements. This results in a Hamming distance of 664. sna simply does not count the cases where there are two edges from A to B in one of the networks and only one in the other.
 T. On 2008.04.19., at 0:36, Simone Gabbriellini wrote:
Gabor,I see the small graphs solution is good for me, it works easy but, compared to hdist in sna package, I have a different results. And even your two solutions bring to different outcomes on the same two networks... it's all about ten/twenty edges more or less:small graphs: 657 hdist (sna): 611 large graphs: 664 I have attached the file for testing, if you have the time. regards, Simone <simulated1.net><empirico.net>igraphhelp mailing list address@hidden http://lists.nongnu.org/mailman/listinfo/igraphhelp_______________________________________________ igraphhelp mailing list address@hidden http://lists.nongnu.org/mailman/listinfo/igraphhelp
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