Plot the subgraph around a Specific Node in a Graph Object

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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

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

Arguments

graphObj

An R object of class graph.

y

(integer) position of the starting node in the adjacency matrix.

dist

Distance of nodes included in subgraph from starting node y.

amat

Precomputed adjacency matrix of type amat.cpdag (optional)

directed

logical indicating if the subgraph should be directed.

main

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

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.

Value

the desired subgraph is plotted and returned via invisible.

Author(s)

Daniel Stekhoven (hoven@stat.math.ethz.ch)

Examples

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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)
}

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