Hello Filippo, By "parallel edges" I meant more than one edge connecting the same two graph vertices. The function works only if this never happens.
Szabolcs On 25 January 2018 at 09:33, Filippo Santi <filippo.sa...@unitn.it> wrote: > Dear Szabolcs, > > Than you for the reply. I will check for these issues you mentioned, even if > I should have created the network without allowing for self loops. Instead, > I don't have clear what you mean for "parallel edges connecting the same two > vertices": is it related with the possibility of having more edge attributes > in the graph or is it related to the multiplexity of the graph? > > Filippo > > 2018-01-23 21:10 GMT+01:00 Szabolcs Horvát <szhor...@gmail.com>: >> >> Hi Filippo, >> >> The message means that your graph has either self-loops (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 <filippo.sa...@unitn.it> 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 >> > >> > >> > >> > _______________________________________________ >> > igraph-help mailing list >> > igraph-help@nongnu.org >> > https://lists.nongnu.org/mailman/listinfo/igraph-help >> > >> >> _______________________________________________ >> igraph-help mailing list >> igraph-help@nongnu.org >> https://lists.nongnu.org/mailman/listinfo/igraph-help > > > > > -- > Filippo Santi > PhD Candidate in Development Economics > > > _______________________________________________ > igraph-help mailing list > igraph-help@nongnu.org > https://lists.nongnu.org/mailman/listinfo/igraph-help > _______________________________________________ igraph-help mailing list igraph-help@nongnu.org https://lists.nongnu.org/mailman/listinfo/igraph-help