regr-tree01

statlearning

trees

tidymodels

string

Published

May 17, 2023

library(tidymodels)

── Attaching packages ────────────────────────────────────── tidymodels 1.1.1 ──

✔ broom        1.0.5     ✔ recipes      1.0.8
✔ dials        1.2.0     ✔ rsample      1.2.0
✔ dplyr        1.1.3     ✔ tibble       3.2.1
✔ ggplot2      3.4.4     ✔ tidyr        1.3.0
✔ infer        1.0.5     ✔ tune         1.1.2
✔ modeldata    1.2.0     ✔ workflows    1.1.3
✔ parsnip      1.1.1     ✔ workflowsets 1.0.1
✔ purrr        1.0.2     ✔ yardstick    1.2.0

── Conflicts ───────────────────────────────────────── tidymodels_conflicts() ──
✖ purrr::discard() masks scales::discard()
✖ dplyr::filter()  masks stats::filter()
✖ dplyr::lag()     masks stats::lag()
✖ recipes::step()  masks stats::step()
• Learn how to get started at https://www.tidymodels.org/start/

Aufgabe

Berechnen Sie einfaches Prognosemodell auf Basis eines Entscheidungsbaums!

Modellformel: am ~ . (Datensatz mtcars)

Berichten Sie die Modellgüte (ROC-AUC).

Hinweise:

Tunen Sie den Komplexitätsparameter des Baumes.
Führen Sie eine \(v=2\)-fache Kreuzvalidierung durch (weil die Stichprobe so klein ist).
Beachten Sie die üblichen Hinweise.

Lösung

Setup

library(tidymodels)
data(mtcars)
library(tictoc)  # Zeitmessung

Für Klassifikation verlangt Tidymodels eine nominale AV, keine numerische:

mtcars <-
  mtcars %>% 
  mutate(am = factor(am))

Daten teilen

d_split <- initial_split(mtcars)
d_train <- training(d_split)
d_test <- testing(d_split)

Modell(e)

mod_tree <-
  decision_tree(mode = "classification",
                cost_complexity = tune())

Rezept(e)

rec1 <- 
  recipe(am ~ ., data = d_train)

Resampling

rsmpl <- vfold_cv(d_train, v = 2)

Workflow

wf1 <-
  workflow() %>%  
  add_recipe(rec1) %>% 
  add_model(mod_tree)

Tuning/Fitting

fit1 <-
  tune_grid(object = wf1,
            resamples = rsmpl)

Bester Kandidat

autoplot(fit1)

show_best(fit1)

Warning: No value of `metric` was given; metric 'roc_auc' will be used.

# A tibble: 5 × 7
  cost_complexity .metric .estimator  mean     n std_err .config              
            <dbl> <chr>   <chr>      <dbl> <int>   <dbl> <chr>                
1   0.0000000194  roc_auc binary       0.5     2       0 Preprocessor1_Model01
2   0.00000000417 roc_auc binary       0.5     2       0 Preprocessor1_Model02
3   0.000107      roc_auc binary       0.5     2       0 Preprocessor1_Model03
4   0.000522      roc_auc binary       0.5     2       0 Preprocessor1_Model04
5   0.00000542    roc_auc binary       0.5     2       0 Preprocessor1_Model05

Finalisieren

wf1_finalized <-
  wf1 %>% 
  finalize_workflow(select_best(fit1))

Warning: No value of `metric` was given; metric 'roc_auc' will be used.

Last Fit

final_fit <- 
  last_fit(object = wf1_finalized, d_split)

collect_metrics(final_fit)

# A tibble: 2 × 4
  .metric  .estimator .estimate .config             
  <chr>    <chr>          <dbl> <chr>               
1 accuracy binary         0.875 Preprocessor1_Model1
2 roc_auc  binary         0.75  Preprocessor1_Model1

Categories:

statlearning
trees
tidymodels
string