Extract Node List from RandomForest Model

Extracts node-level attributes from every tree in a randomForest model. Node IDs match the from/to indices produced by edgelist.randomForest, so the two outputs can be passed directly to igraph::graph_from_data_frame() (after filtering to a single treenum).

Usage

# S3 method for class 'randomForest'
nodelist(input_object, treenum = NULL, ...)

Arguments

input_object

A randomForest model object from the randomForest package

treenum

Integer vector of tree numbers to extract (default: NULL extracts all trees). Values must be between 1 and input_object$ntree.

...

Additional arguments (currently unused)

Value

A data.frame with one row per node (across all trees) and the following columns:

name

Integer node ID within the tree (matches edgelist from/to)

is_leaf

Logical: TRUE for terminal nodes

split_var

Numeric index of the split variable (NA for leaves)

split_var_name

Name of the split variable (NA for leaves)

split_point

Split threshold (NA for leaves)

prediction

Predicted value (numeric for regression, integer class index for classification)

treenum

Integer identifying which tree the node belongs to

label

Display label: "<var>\n< <threshold>" for internal nodes, predicted class name (classification) or numeric value (regression) for leaves

Examples

if (requireNamespace("randomForest", quietly = TRUE)) {
  set.seed(12)
  rf <- randomForest::randomForest(Species ~ ., data = iris, ntree = 3)
  nodes <- nodelist(rf)
  head(nodes)

  # Extract a single tree
  nodes1 <- nodelist(rf, treenum = 1)
}