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Re: [igraph] Anybody ever use igraph to create regression path diagrams?

From: Bernie Hogan
Subject: Re: [igraph] Anybody ever use igraph to create regression path diagrams?
Date: Mon, 16 Jul 2012 23:53:31 +0100

With all due respect to the igraph team, I think this is a pretty cumbersome 
process for igraph. If you get your coefficients in some sort of igraph object 
you can be a lot more flexible in NodeXL (on windows) or gephi. NodeXL is 
probably the best way to customise a graph to taste with pointing and clicking. 
Just write the igraph object to graphml. As for storing the arrangement - save 
the graphml and it should preserve the xy coordinates. 

But if you are a tk hacker by all means try out tamas's suggestions!


Sent from my iPhone

On 16 Jul 2012, at 23:26, Tamás Nepusz <address@hidden> wrote:

> Dear Prof. Johnson,  
> I'm not the developer of the R interface but I thought I'd answer anyway and 
> let Gabor correct or extend what I say.
>> 1. I need to have relatively complicated R objects that are
>> represented by the igraph nodes. For example, a variable may be it
>> 'ordinary' format X, or it may be log(x), or poly(x,d), or so forth.
>> I'm thinking of still calling it X in the graph, but there would be
>> some right-click magic to allow the user to ask for transformations.
>> Is it feasible to add more variables inside a node object. Possible?
>> Can you point me at the right starting point or example?
> Internally, igraph treats the nodes as integers, but it allows you to attach 
> arbitrary R objects as attributes to the nodes (and also to the edges). So, 
> you can probably store all the extra information you need in an appropriately 
> constructed R data type and then attach this to the node as a "data" 
> attribute or something like that. For instance, suppose that you want to 
> store the "type" of a node and the type is one of "ordinary", "log" or "exp". 
> You can then do something like this:
> V(g)$type <- "ordinary"          # assigns "ordinary" to the type of each node
> V(g)[2]$type <- "exp"             # sets the type of node 2 to "exp"
> V(g)$type                      # returns the types of each vertex
> As for the right-click magic: tkplot does not allow the customization of the 
> vertex popup menu yet, but it is probably not too difficult by taking the 
> source code of tkplot() as a template, copying it, and then modifying it as 
> needed (look for the lines starting with tkadd(vertex.popup.menu…)).  
>> 2. Suppose a graph exists, and I view and re-arrange it with tkrplot.
>> Is there a way to make the re-arranged objects take notice of the
>> changes so that they are recorded permanently.
> Again, this can be achieved by modifying the tkplot() function. tkplot() 
> attaches event handlers to several mouse events of the drawing canvas; for 
> instance, the line starting with tkitembind(canvas, tobind, "<B1-Motion>", …) 
> attaches an event handler to the "<B1-Motion>" event, which is fired when the 
> user moves the mouse while button 1 of the mouse is pressed. This corresponds 
> to moving the selected vertices. Adding your own code into the body of the 
> event handler function allows you to respond to the re-arrangement of the 
> nodes.
> Note that tkplot() does not support adding new vertices/edges or removing 
> existing ones (as far as I know), so if the re-arrangements you wish to 
> perform on the graphical representation of the models includes 
> adding/removing vertices or edges, then this definitely needs more coding.
> All the best,
> Tamas
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