Tidy, analyze, and plot causal directed acyclic graphs (DAGs). ggdag uses the powerful dagitty package to create and analyze structural causal models and plot them using ggplot2 and ggraph in a consistent and easy manner.

Installation

You can install ggdag with:

Or you can install the development version from GitHub with:

# install.packages("devtools")
devtools::install_github("malcolmbarrett/ggdag")

Example

ggdag makes it easy to use dagitty in the context of the tidyverse. You can directly tidy dagitty objects or use convenience functions to create DAGs using a more R-like syntax:

library(ggdag)
library(ggplot2)

#  example from the dagitty package
dag <- dagitty::dagitty("dag {
    y <- x <- z1 <- v -> z2 -> y
    z1 <- w1 <-> w2 -> z2
    x <- w1 -> y
    x <- w2 -> y
    x [exposure]
    y [outcome]
  }")

tidy_dag <- tidy_dagitty(dag)

tidy_dag
#> # A DAG with 7 nodes and 12 edges
#> #
#> # Exposure: x
#> # Outcome: y
#> #
#> # A tibble: 13 × 8
#>    name       x      y direction to       xend   yend circular
#>    <chr>  <dbl>  <dbl> <fct>     <chr>   <dbl>  <dbl> <lgl>   
#>  1 v     0.496  -3.40  ->        z1     1.83   -2.92  FALSE   
#>  2 v     0.496  -3.40  ->        z2     0.0188 -2.08  FALSE   
#>  3 w1    1.73   -1.94  ->        x      2.07   -1.42  FALSE   
#>  4 w1    1.73   -1.94  ->        y      1.00   -0.944 FALSE   
#>  5 w1    1.73   -1.94  ->        z1     1.83   -2.92  FALSE   
#>  6 w1    1.73   -1.94  <->       w2     0.873  -1.56  FALSE   
#>  7 w2    0.873  -1.56  ->        x      2.07   -1.42  FALSE   
#>  8 w2    0.873  -1.56  ->        y      1.00   -0.944 FALSE   
#>  9 w2    0.873  -1.56  ->        z2     0.0188 -2.08  FALSE   
#> 10 x     2.07   -1.42  ->        y      1.00   -0.944 FALSE   
#> 11 y     1.00   -0.944 <NA>      <NA>  NA      NA     FALSE   
#> 12 z1    1.83   -2.92  ->        x      2.07   -1.42  FALSE   
#> 13 z2    0.0188 -2.08  ->        y      1.00   -0.944 FALSE

#  using more R-like syntax to create the same DAG
tidy_ggdag <- dagify(
  y ~ x + z2 + w2 + w1,
  x ~ z1 + w1 + w2,
  z1 ~ w1 + v,
  z2 ~ w2 + v,
  w1 ~ ~w2, # bidirected path
  exposure = "x",
  outcome = "y"
) %>%
  tidy_dagitty()

tidy_ggdag
#> # A DAG with 7 nodes and 12 edges
#> #
#> # Exposure: x
#> # Outcome: y
#> #
#> # A tibble: 13 × 8
#>    name      x     y direction to     xend  yend circular
#>    <chr> <dbl> <dbl> <fct>     <chr> <dbl> <dbl> <lgl>   
#>  1 v     -3.58  3.30 ->        z1    -4.05  4.63 FALSE   
#>  2 v     -3.58  3.30 ->        z2    -2.23  3.74 FALSE   
#>  3 w1    -3.03  5.74 ->        x     -3.20  5.14 FALSE   
#>  4 w1    -3.03  5.74 ->        y     -1.98  5.22 FALSE   
#>  5 w1    -3.03  5.74 ->        z1    -4.05  4.63 FALSE   
#>  6 w1    -3.03  5.74 <->       w2    -2.35  4.72 FALSE   
#>  7 w2    -2.35  4.72 ->        x     -3.20  5.14 FALSE   
#>  8 w2    -2.35  4.72 ->        y     -1.98  5.22 FALSE   
#>  9 w2    -2.35  4.72 ->        z2    -2.23  3.74 FALSE   
#> 10 x     -3.20  5.14 ->        y     -1.98  5.22 FALSE   
#> 11 y     -1.98  5.22 <NA>      <NA>  NA    NA    FALSE   
#> 12 z1    -4.05  4.63 ->        x     -3.20  5.14 FALSE   
#> 13 z2    -2.23  3.74 ->        y     -1.98  5.22 FALSE

ggdag also provides functionality for analyzing DAGs and plotting them in ggplot2:

ggdag(tidy_ggdag) +
  theme_dag()

ggdag_adjustment_set(tidy_ggdag, node_size = 14) +
  theme(legend.position = "bottom")

As well as geoms and other functions for plotting them directly in ggplot2:

dagify(m ~ x + y) %>%
  tidy_dagitty() %>%
  node_dconnected("x", "y", controlling_for = "m") %>%
  ggplot(aes(
    x = x,
    y = y,
    xend = xend,
    yend = yend,
    shape = adjusted,
    col = d_relationship
  )) +
  geom_dag_edges(end_cap = ggraph::circle(10, "mm")) +
  geom_dag_collider_edges() +
  geom_dag_point() +
  geom_dag_text(col = "white") +
  theme_dag() +
  scale_adjusted() +
  expand_plot(expand_y = expansion(c(0.2, 0.2))) +
  scale_color_viridis_d(
    name = "d-relationship",
    na.value = "grey85",
    begin = .35
  )

And common structures of bias:


ggdag_butterfly_bias(edge_type = "diagonal")