pDAG hack in ggdag

pdag.r

library(ggdag)
library(ggraph)
library(dplyr)
dag <- confounder_triangle(x_y_associated = TRUE) %>% 
  tidy_dagitty() %>% 
  #  add marker for undirected
  mutate(undirected = ifelse(name == "x" & to == "y", TRUE, FALSE))

#  create a closure function to filter data
filter_undirected <- function(...) {
  function(x) filter(x, ...)
}

dag %>% 
  ggplot(aes(x = x, y = y, xend = xend, yend = yend)) +
    geom_dag_point() + 
    geom_dag_text() +
    geom_dag_edges_link(data = filter_undirected(!undirected)) + 
    #  from ggraph
    geom_edge_link(aes(start_cap = circle(9, "mm"), #shorten edges
                       end_cap = circle(9, "mm")),
                   data = filter_undirected(undirected)) + 
    theme_dag() + 
    scale_dag()