[igraph] knn computation

[Filippo Santi]

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