special case the path for stumps in Cubist

[EmilHvitfeldt]

In reference to tidymodels/orbital#98

library(Cubist)
#> Loading required package: lattice
library(rules)
#> Loading required package: parsnip
library(orbital)

model_df <- modeldata::penguins |> na.omit()

crf_spec <- parsnip::cubist_rules(
  committees = 2,
  max_rules = 5,
  neighbors = 2
) |>
  parsnip::set_engine("Cubist") |>
  parsnip::set_mode("regression")

crf_rec <- recipes::recipe(body_mass_g ~ ., model_df) |>
  recipes::step_dummy(recipes::all_nominal_predictors()) |>
  recipes::step_nzv(recipes::all_predictors())


crf_wkflw <- workflows::workflow() |>
  workflows::add_model(crf_spec) |>
  workflows::add_recipe(crf_rec)

crf_fit <- crf_wkflw |>
  workflows::fit(model_df)

orbital::orbital(crf_fit)
#> 
#> ── orbital Object ──────────────────────────────────────────────────────────────
#> • island_Dream = as.numeric(island == "Dream")
#> • island_Torgersen = as.numeric(island == "Torgersen")
#> • sex_male = as.numeric(sex == "male")
#> • .pred = (ifelse(flipper_length_mm < 202, -320.8 + bill_depth_mm * 64 + ...
#> ────────────────────────────────────────────────────────────────────────────────
#> 4 equations in total.

^{Created on 2025-10-15 with reprex v2.1.1}