 # Radius of nodes in igraph degree()

Hi,

I am using the igraph package in academia and it’s great ! I have two questions regarding the radius or scaling of nodes when using degree(graph, v, mode):

Is the radius of a node simply the square root of the number of its adjacent edges, or is there more damping involved in node growth ?

Where is the radius variable implemented in the source code … can I see it ?

Thank you for helping !

Évariste

I’m not sure I understand the question. Can you give a specific, complete example?

The `vertex.size` option to `plot` specifies the radius of each vertex, not its area. This has nothing to do with where you are getting the sizes from (degrees or elsewhere).

The source of `plot.igraph` is here:

Thank you !

I am specifically interested in the radius, so you are getting me on the right track. I have checked the source, now, and have found in line 282 a variable that looks like the radius of a node: r <- sqrt((cp[,1]-center)**2 + (cp[,2]-center)**2). What I don’t get, right now, is what the (cp[,1]-center)**2 is all about (I am new to R). Any hints ?

You are asking about the source code, but I still don’t understand what the specific problem is. What problem are you trying to solve? Please be specific:

• “I need to accomplish this task”
• “This is the code I tried”
• “This is what it did instead of what I needed”

Oh, right. I am driven by curiosity. I have to present a plot I generated with the degree function, pretty soon, and I expect questions on how the radius of nodes is computed in quantitative terms.

The `degree` function does not plot—it just returns the degrees of vertices. If you want to create a plot in which the radius of each vertex is proportional to its degree, you can use something like

``````g<-erdos.renyi.game(20,20,'gnm')
plot(g, vertex.size=5*degree(g), vertex.label=NA)
``````

Personally, I don’t often use the R interface of igraph, so I may be missing easier ways to do this. I usually work on the C core of igraph and on IGraph/M.

ah, ok. Your example implies that vertex.size is not the area, but is actually the radius of a node. But, Oops, you told me that already My wrong. This was very helpful, indeed !