Extract Node List from rpart Model

Extracts node-level attributes from an rpart model object. Node IDs are the binary heap indices from rownames(input_object$frame) and match the from/to values produced by edgelist.rpart, so the two outputs can be passed directly to igraph::graph_from_data_frame().

Usage

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

Arguments

input_object

An rpart model object from the rpart package

...

Additional arguments (currently unused)

Value

A data.frame with one row per node and the following columns:

name

Integer node ID (binary heap index, matches edgelist from/to)

var

Split variable name, or "<leaf>" for terminal nodes

n

Number of observations routed to this node

dev

Deviance (impurity) at this node

yval

Predicted value (numeric for regression, character class label for classification)

is_leaf

Logical: TRUE for terminal nodes

depth

Integer tree depth (root = 0)

wt

Weighted observation count

complexity

CP pruning parameter at this node

ncompete

Number of competing splits considered

nsurrogate

Number of surrogate splits used

dev_improvement

Numeric deviance reduction from this node's split (NA for leaves)

n_*

(Classification only) One column per class with the count of observations of that class at the node, named n_<classname>. Class names are sanitized via make.names() and lowercased.

prob_*

(Classification only) One column per class with the class probability at that node, named prob_<classname>. Class names are sanitized via make.names() and lowercased.

nodeprob

(Classification only) Proportion of training data reaching this node

label

Display label: "<var>\nn=<n>" for internal nodes, "<yval>\nn=<n>" for leaves

Examples

if (requireNamespace("rpart", quietly = TRUE)) {
  fit <- rpart::rpart(Species ~ Sepal.Length + Sepal.Width, data = iris)
  nodelist(fit)

  # Labels ready for plotting
  nodelist(fit)$label
}
#> [1] "Sepal.Length\nn=150" "Sepal.Width\nn=52"   "setosa\nn=45"       
#> [4] "versicolor\nn=7"     "Sepal.Length\nn=98"  "Sepal.Width\nn=43"  
#> [7] "setosa\nn=7"         "versicolor\nn=36"    "virginica\nn=55"