Load packages

library(tidyverse)
library(ggdag)
library(dagitty)

Define DAG

dag1_str <- 'dag {
  C [pos = "2,2"]
  X [exposure, pos = "1,1"] 
  Y [outcome, pos = "3,1"]
  C -> X
  C -> Y
}'

Plot DAGs

First tidify:

dag1 <- dagitty(dag1_str)

dag1_tidy <- tidy_dagitty(dag1)

dag1_tidy
#> # A DAG with 3 nodes and 2 edges
#> #
#> # Exposure: X
#> # Outcome: Y
#> #
#> # A tibble: 4 x 8
#>   name      x     y direction to     xend  yend circular
#>   <chr> <int> <int> <fct>     <chr> <int> <int> <lgl>   
#> 1 C         2     2 ->        X         1     1 FALSE   
#> 2 C         2     2 ->        Y         3     1 FALSE   
#> 3 X         1     1 <NA>      <NA>     NA    NA FALSE   
#> 4 Y         3     1 <NA>      <NA>     NA    NA FALSE

Then plot:

ggdag(dag1_tidy) + theme_dag()

Equivalence class

ggdag_equivalent_dags(confounder_triangle()) + theme_dag()

ggdag_equivalent_dags(dag1_tidy) + theme_dag()