R function to read a DOT file into an igraph obj

dot.R

library(tidyverse)
library(igraph)

parse_attr <- function(val)
{
  tokens <- 
    str_split(val, '(,)(?=(?:[^"]|"[^"]*")*$)') %>%
    lapply(str_split, '(=)(?=(?:[^"]|"[^"]*")*$)') %>%
    unlist() %>% 
    str_trim() %>%
    str_remove('^"') %>%
    str_remove('"$')
  setNames(tokens[c(F,T)], tokens[c(T,F)]) 
}

read_dot <- function(path)
{
  lines <- read_lines(path) %>% str_trim()
  
  edge <- if(startsWith(lines[1], "digraph")) ">" else "-"
  
  e <-
    str_match(lines, str_c("(\\d+) -", edge, " (\\d+)")) %>%
    as.data.frame() %>%
    filter(complete.cases(.)) %>%
    select(-V1) %>%
    setNames(c("from", "to"))
  
  v <-
    str_match(lines, "(\\d+)\\[(.+)\\]") %>%
    as.data.frame() %>%
    filter(complete.cases(.)) %>%
    select(-V1) %>%
    setNames(c("id", "attr")) %>%
    bind_cols(map_df(lapply(.$attr, parse_attr), bind_rows))
  
  list(v, e)
}

g <- read_dot("/path/to/dot/file.gv")
g <- graph_from_data_frame(g[[2]], vertices = g[[1]])