Alternate plot function for tm with Igraph support.

graphplot <-
function(x,
         terms = sample(Terms(x), 20),
         corThreshold = 0.7,
         weighted=TRUE,
   diag=FALSE,
         ...)
{
    if (system.file(package = "igraph") == "")
        stop("Plotting requires package 'igraph'.")
    m <- if (inherits(x, "TermDocumentMatrix")) t(x) else x
    m <- as.matrix(m[, terms])
    c <- cor(m)
    c[c < corThreshold] <- 0
    c[is.na(c)] <- 0
    diag(c) <- 0
 tmgraph <- graph.adjacency(c, mode=c("undirected"), weighted=TRUE, diag=FALSE,
        add.colnames=NULL, add.rownames=NA)
        plot(tmgraph)
   
    invisible(tmgraph)
}

example usage:
graphplot(dtm,term = freq.terms,corThreshold = 0.5)
dtm- document term matrix
terms- similar to plot.tm
threshold-similar with plot.pm

for saving/export:
agraph <- graphplot(dtm,term = freq.terms,corThreshold = 0.3)
write.graph(agraph,"e:/agraph.graphml", format=c("graphml"))