I would like to lay out graphs (trees) with two types of nodes: boxes and circles.
Is this possible with igraph and how would a minimal example look like?
g <- graph.empty()
g <- add.vertices(g, 4,
label=c('a', 'b', 'c', 'd'),
shape=c('rectangle', 'rectangle', 'circle', 'circle'))
g <- add.edges(g, c(1, 2, 2, 3))