Second event level in weights autoplot

[cgoo4]

Simon hi - I wanted to label autoplot("weights") with the names of the engines. Use of stacks:::top_coefs() was very handy for getting the names!

I was curious though why the weights plot then shows the coefficients for the second factor level rather than the first?

(Reprex based on the vignette example.)

library(tidymodels)
library(stacks)
library(bonsai)

data("tree_frogs")

tree_frogs <- tree_frogs |> 
  select(-c(clutch, latency)) |> 
  mutate(reflex = forcats::fct_other(reflex, keep = "low"))

# First event level = "low"
levels(tree_frogs$reflex)
#> [1] "low"   "Other"

set.seed(1)

tree_frogs_split <- initial_split(tree_frogs)
tree_frogs_train <- training(tree_frogs_split)
tree_frogs_test  <- testing(tree_frogs_split)

folds <- vfold_cv(tree_frogs_train, v = 5)

tree_frogs_rec <- 
  recipe(reflex ~ ., data = tree_frogs_train) |> 
  step_dummy(all_nominal_predictors(), -reflex) |> 
  step_zv(all_predictors())

tree_frogs_wflow <- 
  workflow() |> 
  add_recipe(tree_frogs_rec)

ctrl_grid <- control_stack_grid()

rand_forest_spec <- 
  rand_forest(
    mtry = tune(),
    min_n = tune(),
    trees = 5
  ) |> 
  set_mode("classification") |> 
  set_engine("ranger")

rand_forest_wflow <-
  tree_frogs_wflow |> 
  add_model(rand_forest_spec)

rand_forest_res <- 
  tune_grid(
    object = rand_forest_wflow, 
    resamples = folds, 
    grid = 10,
    control = ctrl_grid
  )
#> i Creating pre-processing data to finalize unknown parameter: mtry

aorsf_spec <- 
  rand_forest(
    mtry = tune(),
    min_n = tune(),
    trees = 500
  ) |> 
  set_mode("classification") |> 
  set_engine("aorsf")

aorsf_wflow <- 
  tree_frogs_wflow |> 
  add_model(aorsf_spec)

aorsf_res <-
  tune_grid(
    object = aorsf_wflow, 
    resamples = folds, 
    grid = 10,
    control = ctrl_grid
  )
#> i Creating pre-processing data to finalize unknown parameter: mtry

tree_frogs_model_st <- 
  stacks() |> 
  add_candidates(rand_forest_res, "ranger") |> 
  add_candidates(aorsf_res, "aorsf") |> 
  blend_predictions() |> 
  fit_members()

# To label the engines
members <- 
  stacks:::top_coefs(
    tree_frogs_model_st, 
    penalty = tree_frogs_model_st$penalty$penalty, 
    n = Inf
    ) |> 
  mutate(member = stringr::str_extract(member, "(?<=_).*(?=_1)"))

# Doesn't show the first event level "low"?
autoplot(tree_frogs_model_st, "weights") + 
  geom_label(
    aes(weight, nrow(members):1, label = member, fill = NULL),
    show.legend = FALSE, hjust = "inward",
    data = members
  )

^{Created on 2024-09-18 with reprex v2.1.1}