Re: [igraph] At structure_generators.c:84 : Invalid (negative) vertex id, Invalid vertex id

[Frederik Elwert]

Hello Stephan,

there were some issues like this on the list: It seems like the error
message is a red herring, and the actual problem is with the
bipartiteness of your graph. I suggested a simple test, and it shows
some issues:

> for (v in V(G)) {
+     vtype <- V(G)[v]$type
+     for (n in neighbors(G, v)) {
+         if (V(G)[n]$type == vtype) {
+             print(paste('Problem with', V(G)[v]$name, 'and',
V(G)[n]$name))
+         }
+     }
+ }
[1] "Problem with 1276601 and 444969570"
[1] "Problem with 1417761 and 444969570"
[1] "Problem with 1600201 and 444969570"
[1] "Problem with 1612811 and 444969570"
[1] "Problem with 1999731 and 444969570"
[1] "Problem with 6467932 and 444969570"
[1] "Problem with 8179472 and 444969570"
[1] "Problem with 8507372 and 444969570"
[1] "Problem with 8560922 and 444969570"
...

So maybe you should double-check your graph is bipartite according to
your "type" attribute. (As I learned here, is.bipartite(g) only checks
if the graph is bipartite according to *any* mapping.) Checking the type
of node 444969570 might be a good start. (I couldn’t test a fixed
mapping, as my machine runs out of memory with bipartite.projection on
your graph.)

Regards
Frederik



Am 25.11.2013 17:45, schrieb Stephan Schlögl:
> Hi,
> I'm using igraph in R. I'm trying to compute:
> 
> /graph <-bipartite.projection(g)/
> 
> but I get the following error:
> 
> /At structure_generators.c:84 : Invalid (negative) vertex id, Invalid
> vertex id/
> 
> this seems strange to me because I'm not using negative vertex ids.
> 
> /> min(V(g)$name)//
> //[1] "100000090"/
> /#(not sure if this is the correct way to prove this, since $name seems
> to be a string)/
> 
> I suppose the only way to make this reproducible is by providing the
> graph object <http://homepage.univie.ac.at/stephan.schloegl/net.RData>
> 
> I would gratefull for any help!
> Best,
> stephan
> 
> 
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