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Query Paths in a DAG

Source: R/query_functions.R
query_paths.Rd

Find all paths between specified nodes in a DAG and determine if they are open or closed given a conditioning set.

Usage

query_paths(
  .tdy_dag,
  from = NULL,
  to = NULL,
  directed = FALSE,
  limit = 100,
  conditioned_on = NULL
)

Arguments

.tdy_dag

A tidy_dagitty or dagitty object

from

Character vector of starting nodes. If NULL, uses exposure from DAG.

to

Character vector of ending nodes. If NULL, uses outcome from DAG.

directed

Logical. If TRUE, only considers directed paths.

limit

Maximum number of paths to return. Default is 100.

conditioned_on

Character vector of variables to condition on.

Value

A tibble with columns:

  • path_id: Integer identifier for each path

  • from: Starting node

  • to: Ending node

  • path: Character string representation of the path

  • path_type: Character classification as "direct" (a directed causal path), "backdoor" (a path whose first edge points into from), or "other" (any other path, such as one through a collider)

  • variables: List column containing all variables in the path

  • open: Logical indicating if the path is open

Details

When from or to has more than one element, paths are enumerated once for each ordered pair of endpoints and the results are stacked, so every row names the pair its path runs between.

Examples

library(ggdag)
dag <- dagify(
  y ~ x + z,
  x ~ w,
  z ~ w,
  exposure = "x",
  outcome = "y"
)

query_paths(dag)
#> # A tibble: 2 × 7
#>   path_id from  to    path             path_type variables open 
#>     <int> <chr> <chr> <chr>            <chr>     <list>    <lgl>
#> 1       1 x     y     x -> y           direct    <chr [2]> TRUE 
#> 2       2 x     y     x <- w -> z -> y backdoor  <chr [4]> TRUE 
query_paths(dag, conditioned_on = "z")
#> # A tibble: 2 × 7
#>   path_id from  to    path             path_type variables open 
#>     <int> <chr> <chr> <chr>            <chr>     <list>    <lgl>
#> 1       1 x     y     x -> y           direct    <chr [2]> TRUE 
#> 2       2 x     y     x <- w -> z -> y backdoor  <chr [4]> FALSE