graph2T Conversions "graph" (sparse) Matrix

Description

The Matrix package has supported conversion from and to "graph" objects from (Bioconductor) package graph since summer 2005, via the usual as(., "<class>") coercion,

  as(from, Class)

Since 2013, this functionality is further exposed as the graph2T() and T2graph() functions (with further arguments than just from), which convert graphs to and from the triplet form of sparse matrices (of class "TsparseMatrix") .

Usage

graph2T(from, use.weights = )
T2graph(from, need.uniq = is_not_uniqT(from), edgemode = NULL)

Arguments

from	for graph2T(), an R object of class "graph"; for T2graph(), a sparse matrix inheriting from "TsparseMatrix".
use.weights	logical indicating if weights should be used, i.e., equivalently the result will be numeric, i.e. of class dgTMatrix; otherwise the result will be ngTMatrix or nsTMatrix, the latter if the graph is undirected. The default looks if there are weights in the graph, and if any differ from 1, weights are used.
need.uniq	a logical indicating if from may need to be internally “uniqified”; do not set this and hence rather use the default, unless you know what you are doing!
edgemode	one of NULL, "directed", or "undirected". The default NULL looks if the matrix is symmetric and assumes "undirected" in that case.

Value

For graph2T(), a sparse matrix inheriting from "TsparseMatrix".

For T2graph() an R object of class "graph".

See Also

Note that the CRAN package igraph also provides conversions from and to sparse matrices (of package Matrix) via its graph.adjacency() and get.adjacency().

Examples

if(isTRUE(try(require(graph)))) { ## super careful .. for "checking reasons"
  n4 <- LETTERS[1:4]; dns <- list(n4,n4)
  show(a1 <- sparseMatrix(i= c(1:4),   j=c(2:4,1),   x = 2,    dimnames=dns))
  show(g1 <- as(a1, "graph")) # directed
  unlist(edgeWeights(g1)) # all '2'

  show(a2 <- sparseMatrix(i= c(1:4,4), j=c(2:4,1:2), x = TRUE, dimnames=dns))
  show(g2 <- as(a2, "graph")) # directed
  # now if you want it undirected:
  show(g3  <- T2graph(as(a2,"TsparseMatrix"), edgemode="undirected"))
  show(m3 <- as(g3,"Matrix"))
  show( graph2T(g3) ) # a "pattern Matrix" (nsTMatrix)

  a. <- sparseMatrix(i= 4:1, j=1:4, dimnames=list(n4,n4), giveC=FALSE) # no 'x'
  show(a.) # "ngTMatrix"
  show(g. <- as(a., "graph"))

}