## Generate data.
set.seed(1986)
n <- 3000
k <- 3
X <- matrix(rnorm(n * k), ncol = k)
colnames(X) <- paste0("x", seq_len(k))
Y <- exp(X[, 1]) + 2 * X[, 2] * X[, 2] > 0 + rnorm(n)
## Construct tree.
library(rpart)
tree <- rpart(Y ~ ., data = data.frame(Y, X))
## Extract number of leaves.
n_leaves <- get_leaves(tree)
n_leaves
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