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

[Paul Johnson]

Hello, igraph!

I've been looking around for quite a while for a good way to allow
regression modelers to view diagrams of regression models, and then
possibly add variables or remove them from a graphical setup, and then
execute a regression again.  I started monitoring igraph years ago
because I was doing network analysis, but did not think of igraph from
this perspective.  Today I realized that a regression path model is a
directed graph.  igraph can draw some graphs and I can re-arrange
nodes and edges with tkrplot.

Maybe an igraph graph object can become the over-arching structure in
my regression mission.  Could I ask for your ideas?

The part I can't quite imagine is the "round trip" from a graph object
to a graph drawing with which the user interacts, back into a graph
object that can then re-estimate a regression model.

I am not aware of any use of igraph to achieve this same purpose.
There is a package called "qgraph" that implements its own versions of
some of igraph's node placement algorithms, but it has some internal
features that make it difficult to extend for my purposes.  Since
igraph already has a nice set of constructs for drawing graphs, along
with the node placement algorithms, it appears to me igraph might be
the right place to start.

Initial questions.

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?

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.

Or, if that's impossible, what other GUI ways are there to interact
with nodes to tell them to draw themselves in a different position
(and to take their edges with them).

I'm sorry if these are too elementary questions. I'm just getting started.

PJ

-- 
Paul E. Johnson
Professor, Political Science    Assoc. Director
1541 Lilac Lane, Room 504     Center for Research Methods
University of Kansas               University of Kansas
http://pj.freefaculty.org            http://quant.ku.edu