[igraph] mycircle and arrows

[Ted Toal]

The example "mycircle" custom vertex with customizable thickness of borders, posted 15 Mar 2013, has a problem when edges are directed: the arrows are covered by the node circles.  The arrow tip appears to end at the center of the circle.  How might I fix this?

Ted Toal

library(igraph)

mycircle <- function(coords, v=NULL, params) {

  vertex.color <- params("vertex", "color")

  if (length(vertex.color) != 1 && !is.null(v)) {

    vertex.color <- vertex.color[v]

  }

  vertex.size  <- 1/200 * params("vertex", "size")

  if (length(vertex.size) != 1 && !is.null(v)) {

    vertex.size <- vertex.size[v]

  }

  vertex.frame.color <- params("vertex", "frame.color")

  if (length(vertex.frame.color) != 1 && !is.null(v)) {

    vertex.frame.color <- vertex.frame.color[v]

  }

  vertex.frame.width <- params("vertex", "frame.width")

  if (length(vertex.frame.width) != 1 && !is.null(v)) {

    vertex.frame.width <- vertex.frame.width[v]

  }

  

  mapply(coords[,1], coords[,2], vertex.color, vertex.frame.color,

         vertex.size, vertex.frame.width,

         FUN=function(x, y, bg, fg, size, lwd) {

           symbols(x=x, y=y, bg=bg, fg=fg, lwd=lwd,

                   circles=size, add=TRUE, inches=FALSE)

         })

}

add.vertex.shape("fcircle", clip=igraph.shape.noclip,

 plot=mycircle, parameters=list(vertex.frame.color=1,

                                  vertex.frame.width=1))

g=graph.formula(A-+B,B-+C)

layout=matrix(c(2,1, 1,0, 3,0),byrow=TRUE,nrow=3)

plot.igraph(g,layout=layout,edge.color="black",vertex.color="white", vertex.label=c("A","B","C"),vertex.size=20,vertex.label.cex=3, vertex.label.color="black",vertex.shape="fcircle",

                     vertex.frame.color="black",edge.width=3,edge.arrow.size=1.2,edge.arrow.width=1.2)