pcalg (version 2.0-3)

plotSG: Plot the subgraph around a Specific Node in a Graph Object

Description

Plots a subgraph for a specified starting node and a given graph. The subgraph consists of those nodes that can be reached from the starting node by passing no more than a specified number of edges.

Usage

plotSG(graphObj, y, dist, amat = NA, directed = TRUE, main = )

Arguments

graphObj

An Robject of class graph.

y

Starting node.

dist

Distance of nodes included in subgraph from starting node y.

amat

Adjacency matrix of skeleton graph (optional).

directed

logical indicating if the subgraph should be directed.

main

Title to be used, with a sensible default; see title.

Value

• the desired subgraph is plotted and returned via invisible.

Details

Commencing at the starting point y the function looks for the neighbouring nodes. Beginning with direct parents and children it will continue hierarchically through the distances to y. If directed is true (as per default), the orientation of the edges is taken from the initial graph.

The package Rgraphviz must be installed, and is used for the plotting.

Examples

if (require(Rgraphviz)) {
## generate a random DAG:
p <- 10
set.seed(45)
myDAG <- randomDAG(p, prob = 0.3)

## plot whole the DAG
plot(myDAG, main = "randomDAG(10, prob = 0.3)")

op <- par(mfrow = c(3,2))
## plot the neighbours of node number 8 up to distance 1
plotSG(myDAG, 8, 1, directed = TRUE)
plotSG(myDAG, 8, 1, directed = FALSE)

## plot the neighbours of node number 8 up to distance 2
plotSG(myDAG, 8, 2, directed = TRUE)
plotSG(myDAG, 8, 2, directed = FALSE)

## plot the neighbours of node number 8 up to distance 3
plotSG(myDAG, 8, 3, directed = TRUE)
plotSG(myDAG, 8, 3, directed = FALSE)

## Note that the layout of the subgraph might be different than in the
## original graph, but the graph structure is identical
par(op)
}