Re: [igraph] extracting x y values from an igraph object to plot in ggplot

[Gábor Csárdi]

Hi,

On Mon, Jun 11, 2012 at 10:36 AM, Roey Angel <address@hidden> wrote:
> Hi,
> I'd like to extract the x y values from an igraph object in order to plot it
> in ggplot (which accepts only data frames).

there are not x y values in igraph objects, at least not by default.

> Scott Chamberlain has published an attempt to plot igraph networks in ggplot
> (http://schamberlain.github.com/2011/03/basic-ggplot2-network-graphs/) but
> he's just generating random values for the position of the vertices (through
> the vplace variable).
> This works fine for small networks but makes a clutter in large networks
> and, most importantly, doesn't allow drawing different layouts.

You can generate layout coordinates by using one of the several layout
functions, e.g.
xy <- layout.fruchterman.reingold(mygraph)

> The reason I'm insisting on ggplot (apart from the fact that this is what I
> know best in R graphics) is because I'd like to have the vertices sized
> according to a vector of numeric values and their colours according to a
> character vector and that's done very easly in ggplot.

This is actually quite easy without ggplot as well:

G <- graph.ring(10)
plot(G, vertex.size=1:10*2, vertex.color=rainbow(10), layout=layout.circle)

Best,
Gabor

> I'm a beginner and trying to figure out my way in the world of networks and
> igraph so there might be something very basic I'm missing out here.
>
> Thanks a lot in advance,
> Roey
>
>
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-- 
Gabor Csardi <address@hidden>     MTA KFKI RMKI