Re: [igraph] Graph attributes in R and C

[Matthew Walker]

On 10-10-19 08:24 PM, Gábor Csárdi wrote:
> Hi Matthew,
>
> On Wed, Oct 20, 2010 at 2:00 AM, Matthew Walker
> <address@hidden>  wrote:
> [...]
>    
>
> > Thus, I guess my question is: Is there a correct way to do what I am trying
> > to do?  Is there a way to convert an R-based-graph-with-attributes to a
> > C-based-graph-with-attributes?  What would you do?
> >      
> You can pass the graph attributes that are important to your C
> function separately, as regular arguments. The R->C glue code can take
> care of this.
>
> Another option is to use the R attribute handler from C, see the code
> in foreign.c for examples. E.g. the pajek exporter writes the
> attributes into the output file, even if they are defined in R.
> Currently only numeric and string attributes are supported here.

Thank you very much for your help.  It was very useful to have confirmed 
that this was indeed the problem.  In the end I decided that, given it 
was just for debug/testing, I could use a "standard" interface: 
write.graph() and igraph_read_graph_graphml() ... thus converting from 
R-with-attributes to C-with-attributes ;o)

However, thanks again for your help.

In the process of doing this, I have discovered something interesting 
though:

This writes out an attribute for each vertex:
> library(igraph)
> g <- erdos.renyi.game(5, 1.0)
> V(g)$has_sensor <- 1
> write.graph(g,"test.graphml","graphml")

But this doesn't!
> library(igraph)
> g <- erdos.renyi.game(5, 1.0)
> V(g)$has_sensor <- TRUE
> write.graph(g,"test.graphml","graphml")


Thanks again for everything,

Matthew