Plotting graphs

Within R, the library igraph provides a neat way to store, manipulate, analyse and plot graph datastructures. 

install.packages('igraph')

library('igraph')

An undirected cycle graph on four vertices can be made like so:

g <- make_ring(4)

Then we can plot out the graph using igraph's default settings:

plot(g)

The position of the various nodes can be fixed using g$layout

g$layout <- matrix(

  c(1,1, 1,2, 2,2, 2,1), 

  ncol = 2,

  byrow = TRUE

  )

So the first node would be at (1,1), the second at (1,2) etc; and upon plotting, the graph edges are now aligned to the axes:

plot(g)

The images are good enough for me at the moment, although I'm not keen on base-R graphics. Fortunately, someone else has already sussed out how to plot igraphs with ggplot2.