R: Convert between directed and undirected graphs

as.directed {igraph}

R Documentation

Convert between directed and undirected graphs

Description

as.directed converts an undirected graph to directed, as.undirected does the opposite, it converts a directed graph to undirected.

Usage

as.directed(graph, mode = c("mutual", "arbitrary")) 
as.undirected(graph, mode = c("collapse", "each", "mutual"),
       edge.attr.comb = getIgraphOpt("edge.attr.comb"))

Arguments

`graph`	The graph to convert.
`mode`	Character constant, defines the conversion algorithm. For `as.directed` it can be `mutual` or `arbitrary`. For `as.undirected` it can be `each`, `collapse` or `mutual`. See details below.
`edge.attr.comb`	Specifies what to do with edge attributes, if `mode="collapse"` or `mode="mutual"`. In these cases many edges might be mapped to a single one in the new graph, and their attributes are combined. Please see `attribute.combination` for details on this.

Details

Conversion algorithms for as.directed:

arbitrary: The number of edges in the graph stays the same, an arbitrarily directed edge is created for each undirected edge.
mutual: Two directed edges are created for each undirected edge, one in each direction.

Conversion algorithms for as.undirected:

each: The number of edges remains constant, an undirected edge is created for each directed one, this version might create graphs with multiple edges.
collapse: One undirected edge will be created for each pair of vertices which are connected with at least one directed edge, no multiple edges will be created.
mutual: One undirected edge will be created for each pair of mutual edges. Non-mutual edges are ignored. This mode might create multiple edges if there are more than one mutual edge pairs between the same pair of vertices.

Value

A new graph object.

Author(s)

Gabor Csardi csardi.gabor@gmail.com

Examples

g <- graph.ring(10)
as.directed(g, "mutual")
g2 <- graph.star(10)
as.undirected(g)

# Combining edge attributes
g3 <- graph.ring(10, directed=TRUE, mutual=TRUE)
E(g3)$weight <- seq_len(ecount(g3))
ug3 <- as.undirected(g3)
print(ug3, e=TRUE)
## Not run: 
  x11(width=10, height=5)
  layout(rbind(1:2))
  plot( g3, layout=layout.circle, edge.label=E(g3)$weight)
  plot(ug3, layout=layout.circle, edge.label=E(ug3)$weight)

## End(Not run)

g4 <- graph(c(1,2, 3,2,3,4,3,4, 5,4,5,4,
              6,7, 7,6,7,8,7,8, 8,7,8,9,8,9,
              9,8,9,8,9,9, 10,10,10,10))
E(g4)$weight <- seq_len(ecount(g4))
ug4 <- as.undirected(g4, mode="mutual",
              edge.attr.comb=list(weight=length))
print(ug4, e=TRUE)

[Package igraph version 0.7.0 Index]