Matrics to Graph coersions {graph}R Documentation

Coercing matrices to graphs

Description

A collection of functions and methods to convert various forms of matrices into graph objects.

Usage

aM2bpG(aM)
ftM2adjM(ft, W=NULL, V=NULL, edgemode="directed")

Arguments

ft A matrix with two columns containing the from/to representation of graph edges.
W An optional vector of edge weights.
V An optional vector of node names.
aM An affiliation matrix for a bipartite graph.
edgemode Specifies if the resulting graph is to be directed or undirected

Details

In the fuction ftM2adjM, a from/to matrix is converted into an adjacency matrix (which can then be coerced directly into a graphNEL-class with as. Ths first column of the ft represents the from nodes and the second column represents to nodes. This representation does not allow for unconnected nodes except with the V argument (see below). The edgemode parameter can be used to specify if the desired output is a directed or undirected graph.

Also in ftM2adjM, W is an optional vector of edge weights. The order of the edge weights in the vector should correspond to the order of the edges recorded in L. If it is not specified, edge weights of 1 are assigned by default. The V argument is an optional vector of node names. All nodes in ft must be contained in V, but not all nodes in V must be contained in ft. If V is not specified, it is set to all nodes represented in ft or M. Specifying V is most useful for creating a graph that includes nodes with degree 0.

aM is an affiliation matrix as frequently used in social networks analysis. The rows of aM represent actors, and the columns represent events. An entry of "1" in the ith row and jth column represents affiliation of the ith actor with the jth event. Weighted entries may also be used. aM2bpG returns a graphNEL object with nodes consisting of the set of actors and events, and directed (possibly weighted) edges from the actors to their corresponding events. If plotted using Rgraphviz and the dot layout, the bipartite structure of the graph returned by aM2bpG should be evident.

An adjacency matrix can be directly coerced into a graphNEL using the as method. If the matrix is a symmetric matrix, then the resulting graph will be undirected, otherwise it will be directed.

Value

For aM2bpG, an object of class graphNEL. For ftM2adjM, an adjacency matrix representation of the coerced graph.

Author(s)

Denise Scholtens

Examples

From <- c("A","A","C","C")
To <- c("B","C","A","D")
L <- cbind(From,To)

W <- 1:4
M1 <- ftM2adjM(L,W, edgemode="undirected")
M2 <- ftM2adjM(L)

G1 <- as(M1, "graphNEL")
G2 <- as(M2, "graphNEL")

[Package Contents]