add.edges: Add Edges to a Network Object

Description

Add one or more edges to an existing network object.

Usage

add.edge(x, tail, head, names.eval=NULL, vals.eval=NULL,  edge.check=FALSE, ...)
add.edges(x, tail, head, names.eval=NULL, vals.eval=NULL, ...)

Arguments

an object of class network

tail

for add.edge, a vector of vertex IDs reflecting the tail set for the edge to be added; for add.edges, a list of such vectors

head

for add.edge, a vector of vertex IDs reflecting the head set for the edge to be added; for add.edges, a list of such vectors

names.eval

for add.edge, an optional list of names for edge attributes; for add.edges, a list of length equal to the number of edges, with each element containing a list of names for the attributes of the corresponding edge

vals.eval

for add.edge, an optional list of edge attribute values (matching names.eval); for add.edges, a list of such lists

edge.check

logical; should we perform (computationally expensive) tests to check for the legality of submitted edges?

...

additional arguments

Value

Invisibly, add.edge and add.edges return pointers to their modified arguments; both functions modify their arguments in place..

Details

The edge checking procedure is very slow, but should always be employed when debugging; without it, one cannot guarantee that the network state is consistent with network level variables (see network.indicators). For example, by default it is possible to add multiple edges to a pair of vertices.

Edges can also be added/removed via the extraction/replacement operators. See the associated man page for details.

References

Butts, C. T. (2008). “network: a Package for Managing Relational Data in R.” Journal of Statistical Software, 24(2). http://www.jstatsoft.org/v24/i02/

Examples

Run this code

#Initialize a small, empty network
g<-network.initialize(3)

#Add an edge
add.edge(g,1,2)
g

#Can also add edges using the extraction/replacement operators
#note that replacement operators are much slower than add.edges()
g[,3]<-1
g[,]

#Add multiple edges with attributes to a network

# pretend we just loaded in this data.frame from a file
# Note: network.edgelist() may be simpler for this case
elData<-data.frame(
  from_id=c("1","2","3","1","3","1","2"),
  to_id=c("1", "1", "1", "2", "2", "3", "3"),
  myEdgeWeight=c(1, 2, 1, 2, 5, 3, 9.5),
  someLetters=c("B", "W", "L", "Z", "P", "Q", "E"),
  edgeCols=c("red","green","blue","orange","pink","brown","gray"),
  stringsAsFactors=FALSE
)

valueNet<-network.initialize(3,loops=TRUE)

add.edges(valueNet,elData[,1],elData[,2],
    names.eval=rep(list(list("myEdgeWeight","someLetters","edgeCols")),nrow(elData)), 
    vals.eval=lapply(1:nrow(elData),function(r){as.list(elData[r,3:5])}))

list.edge.attributes(valueNet)

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