Extract Edgelist from rpart Model

Converts an rpart model object into a network edgelist representation. The rpart package uses binary heap numbering for node IDs (root = 1, left child of k = 2k, right child of k = 2k + 1), so parent-child edges are derived directly from the node IDs in rownames(input_object$frame).

Usage

# S3 method for class 'rpart'
edgelist(input_object, ...)

Arguments

input_object

An rpart model object from the rpart package

...

Additional arguments (currently unused)

Value

A data.frame with the following columns:

from

Parent node ID (binary heap index)

to

Child node ID (binary heap index)

label

Split condition label from labels()

split_var

Variable name used for the split

split_op

Operator: "<" or ">=" for numeric splits, NA for categorical splits

split_point

Numeric threshold for the split (NA for categorical splits)

Details

Edge labels come from labels(input_object, collapse = TRUE), which correctly handles the ncat sign that controls split direction (left child does not always get "<").

Examples

if (requireNamespace("rpart", quietly = TRUE)) {
  fit <- rpart::rpart(Species ~ ., data = iris)
  el <- edgelist(fit)
  head(el)

  # Parsed split components
  el[, c("split_var", "split_op", "split_point")]
}
#>      split_var split_op split_point
#> 1 Petal.Length        <        2.45
#> 2 Petal.Length       >=        2.45
#> 3  Petal.Width        <        1.75
#> 4  Petal.Width       >=        1.75