Re: [igraph] Node attributes

[Tamas Nepusz]

> 1). Whenever a graph in "ncol" format is read by igraph the vertex  
> names are converted into numbers. So my question is how is the node  
> numbering sequence determined i.e which node is numbered as 1 and so  
> on ?
I think igraph processes the file top-down, and whenever it finds a  
node that was not seen before, igraph assigns the next available ID to  
the node. So, in your case, eco:b4069 will be node 0, eco:b1241 will  
be node 1, eco:b0115 will be node 2 and so on. But you shouldn't rely  
on that as the behaviour might change in future releases. Check the  
"name" vertex attribute of the loaded graph instead, it will contain  
the original node IDs. If you are using R, you will have to load your  
graph as follows:

> g <- read.graph("my_graph.ncol")
> V(g)$name

> 2). I want to get the node property (degree, betweenness etc.)  
> against the node name as a list after various graph calculatons are  
> done. How do I do it ?
E.g., for degree and betweenness:

> df <- data.frame(degree=degree(g), betweenness=betweenness(g),  
row.names=V(g)$name)

Then you get a data frame with columns "degree" and "betweenness", and  
the row names contain the names of the corresponding vertices.

In Python, you can achieve something similar by:

>>> df = zip(g.vs["name"], g.degree(), g.betweenness())

This will be a list of triplets.

--
Tamas