Description

R function for drawing a DAG (directed acyclic graph). Though similar R functions or packages exist, they require specification of the DAG using knowing dot (Graphviz) or Mermaid. In comparison, this function requires specification of the DAG using R objects.

Dependencies

• DiagrammeR

Use

Define the nodes, as a list. The list should contain one or more character vector, with named elements. Each character vector defines a row in the desired DAG. For example:

nodes<-list(
  c(
    age='Age',
    sex='Sex'
  ),
  c(
    x='Exposure',
    y='Outcome'  
  ),
  c(
    selection='Selection'
  )
)

Here, there are 3 character vectors, indicating we want 3 rows. The first character vector defines two nodes, age and sex, with the display names "Age" and "Sex."

Define the arrows as a list. The list should contain one or more character vector. Each character vector defines an arrow. For example:

arrows<-list(
  c('x','y','blue'),
  c('age','x'),
  c('age','y'),
  c('sex','x'),
  c('sex','y'),
  c('x','selection','red'),
  c('y','selection','red')
)

The first character vector defines an arrow that begins from x and ends with y, and will be blue. A full list of possible colors is available here.

Define node colors as a list, with named elements. The list should contain one or more character vector. For example:

node_colors<-list(
  powderblue=c('x','y'),
  pink='selection'
)

The first element indicates that we want x and y to be powderblue.

To draw the DAG:

draw_a_dag(nodes,arrows,node_colors)

The resulting image is:

Unfortunately, the underlying function does not work with cairo_pdf(). To export to PDF, use the DiagrammeRsvg and rsvg packages:

rsvg_pdf(charToRaw(export_svg(draw_a_dag(nodes,arrows,node_colors))),'example.pdf')