Plotting texts as graphs with R and igraph

August 4, 2010

(This article was first published on Cornelius Puschmann's Blog » R, and kindly contributed to R-bloggers)

I’ve plotted several word association graphs for this New York Times article (1st paragraph) using R and the igraph library.

#1, random method

#2, circle method

#3, sphere method

#4, spring method

#5, fruchterman-reingold method

# 6, kamada-kawai method

#7, graphopt method

The red vertices mark cliques. Here’s the (rough) R code for plotting such graphs:

rm(list=ls());


library("igraph");

library("Cairo");
# read parameters

print("Text-as-Graph for R 0.1");

print("------------------------------------");
print("Path (no trailing slash): ");

datafolder <- scan(file="", what="char");
print("Text file: ");

datafile <- scan(file="", what="char");
txt <- scan(paste(datafolder, datafile, sep="/"), what="char", sep="\n", encoding="UTF-8");
print("Width/Height (e.g. 1024x768): ");

res <- scan(file="", what="char");

rwidth <- unlist(strsplit(res, "x"))[1]

rheight <- unlist(strsplit(res, "x"))[2]
words <- unlist(strsplit(gsub("[[:punct:]]", " ", tolower(txt)), "[[:space:]]+"));
g.start <- 1;
g.end <- length(words) - 1;
assocs <- matrix(nrow=g.end, ncol=2)
for (i in g.start:g.end)

{

	assocs[i,1] <- words[i];

	assocs[i,2] <- words[i+1];

	print(paste("Pass #", i, " of ", g.end, ". ", "Node word is ", toupper(words[i]), ".", sep=""));

}
print("Build graph from data frame...");

g.assocs <- graph.data.frame(assocs, directed=F);
print("Label vertices...");

V(g.assocs)$label <- V(g.assocs)$name;
print("Associate colors...");

V(g.assocs)$color <- "Gray";
print("Find cliques...");

V(g.assocs)[unlist(largest.cliques(g.assocs))]$color <- "Red";
print("Plotting random graph...");

CairoPNG(paste(datafolder, "/", "text-igraph-random.png", sep=""), width=as.numeric(rwidth), height=as.numeric(rheight));

plot(g.assocs, layout=layout.random, vertex.size=4, vertex.label.dist=0);

dev.off();
print("Plotting circle graph...");

CairoPNG(paste(datafolder, "/", "text-igraph-circle.png", sep=""), width=as.numeric(rwidth), height=as.numeric(rheight));

plot(g.assocs, layout=layout.circle, vertex.size=4, vertex.label.dist=0);

dev.off();
print("Plotting sphere graph...");

CairoPNG(paste(datafolder, "/", "text-igraph-sphere.png", sep=""), width=as.numeric(rwidth), height=as.numeric(rheight));

plot(g.assocs, layout=layout.sphere, vertex.size=4, vertex.label.dist=0);

dev.off();
print("Plotting spring graph...");

CairoPNG(paste(datafolder, "/", "text-igraph-spring.png", sep=""), width=as.numeric(rwidth), height=as.numeric(rheight));

plot(g.assocs, layout=layout.spring, vertex.size=4, vertex.label.dist=0);

dev.off();
print("Plotting fruchterman-reingold graph...");

CairoPNG(paste(datafolder, "/", "text-igraph-fruchterman-reingold.png", sep=""), width=as.numeric(rwidth), height=as.numeric(rheight));

plot(g.assocs, layout=layout.fruchterman.reingold, vertex.size=4, vertex.label.dist=0);

dev.off();
print("Plotting kamada-kawai graph...");

CairoPNG(paste(datafolder, "/", "text-igraph-kamada-kawai.png", sep=""), width=as.numeric(rwidth), height=as.numeric(rheight));

plot(g.assocs, layout=layout.kamada.kawai, vertex.size=4, vertex.label.dist=0);

dev.off();
#CairoPNG(paste(datafolder, "/", "text-igraph-reingold-tilford.png", sep=""), width=as.numeric(rwidth), height=as.numeric(rheight));

#plot(g.assocs, layout=layout.reingold.tilford, vertex.size=4, vertex.label.dist=0);

#dev.off();
print("Plotting graphopt graph...");

CairoPNG(paste(datafolder, "/", "text-igraph-graphopt.png", sep=""), width=as.numeric(rwidth), height=as.numeric(rheight));

plot(g.assocs, layout=layout.graphopt, vertex.size=4, vertex.label.dist=0);

dev.off();