
From:  Filippo Santi 
Subject:  Re: [igraph] knn computation 
Date:  Thu, 25 Jan 2018 09:33:49 +0100 
Hi Filippo,
The message means that your graph has either selfloops (an edge
connecting a vertex to itself), or parallel edges connecting the same
two vertices. The function does not work on such graphs. You need to
supply a simple graph—take a look at simplify().
Also, be aware that knn() does not compute the mean neighbour strength
for weighted graphs. https://github.com/igraph/igraph/issues/987
Szabolcs
> ______________________________
On 23 January 2018 at 19:29, Filippo Santi <address@hidden> wrote:
> Dear all,
>
> I am new to R and even more to igraph. I am working on foreign direct
> investment network, and I am currently trying to compute average nearest
> neighbour degree and average nearest neighbour strength, using the knn
> function. My code is as following:
>
> fdi.graph.2003 < graph_from_data_frame(fdi.edge.2003, directed = T,
> vertices = fdi.attr.2003)
> ANND < knn(fdi.graph.2003)
>
> However, R returns the following error message
>
> Error in knn(fdi.graph.2003) :
> At structural_properties.c:5889 : Average nearest neighbor degree Works only
> with simple graphs, Invalid value
>
> Do you have any explanation to try to solve this issue? I tried to compute
> it building the graph from a simple binary edgelist too (the above message
> comes from computations based on a weighted network with plenty of edge
> attributes, built from a data.frame) but it is not working either.
>
>
> Thanks for any help,
>
>
> Filippo
>
>
>
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