2. Diagnostic Workflow

In E2E: Ensemble Learning Framework for Diagnostic and Prognostic Modeling

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

library(E2E)

# Set up a 2-core cluster for parallel processing in this vignette
# This is crucial for passing R CMD check on CI/CD platforms
cl <- parallel::makeCluster(2)
doParallel::registerDoParallel(cl)

Diagnostic Models (Classification)

This track is dedicated to binary classification tasks.

1. Initialization

First, initialize the diagnostic modeling system. This registers all built-in classification models.

initialize_modeling_system_dia()

2. Training Single Models with models_dia

The models_dia function is the gateway to training one or more standard classification models.

Basic Usage

By default, models_dia runs all registered models. For this demonstration, we'll run a subset to save time.

# To run all, use model = "all_dia" or omit the parameter.
results_all_dia <- models_dia(train_dia, model = c("rf", "lasso", "xb"))

# Print a summary for a specific model (e.g., Random Forest)
print_model_summary_dia("rf", results_all_dia$rf)

Advanced Usage & Customization

You can precisely control the modeling process by specifying parameters.

# Run a specific subset of models with tuning enabled and custom thresholds
results_dia_custom <- models_dia(
  data = train_dia,
  model = c("rf", "lasso", "xb"),
  tune = TRUE,
  seed = 123,
  threshold_choices = list(rf = "f1", lasso = 0.6, xb = "youden"),
  positive_label_value = 1,
  negative_label_value = 0,
  new_positive_label = "Case",
  new_negative_label = "Control"
)

# View the custom results
print_model_summary_dia("rf", results_dia_custom$rf)

3. Ensemble Modeling

Bagging (bagging_dia)

Builds a Bagging ensemble by training a base model on multiple bootstrap samples.

# Create a Bagging ensemble with XGBoost as the base model
# n_estimators is reduced for faster execution in this example.
bagging_xb_results <- bagging_dia(train_dia, base_model_name = "xb", n_estimators = 5)
print_model_summary_dia("Bagging (XGBoost)", bagging_xb_results)

Voting (voting_dia)

Combines predictions from multiple pre-trained models.

# Create a soft voting ensemble from the top models
voting_soft_results <- voting_dia(
  results_all_models = results_all_dia,
  data = train_dia,
  type = "soft"
)
print_model_summary_dia("Voting (Soft)", voting_soft_results)

Stacking (stacking_dia)

Uses predictions from base models as features to train a final meta-model.

# Create a Stacking ensemble with Lasso as the meta-model
stacking_lasso_results <- stacking_dia(
  results_all_models = results_all_dia,
  data = train_dia,
  meta_model_name = "lasso"
)
print_model_summary_dia("Stacking (Lasso)", stacking_lasso_results)

Handling Imbalanced Data (imbalance_dia)

Implements the EasyEnsemble algorithm.

# Create an EasyEnsemble with XGBoost as the base model
# n_estimators is reduced for faster execution.
results_imbalance_dia <- imbalance_dia(train_dia, base_model_name = "xb", n_estimators = 5, seed = 123)
print_model_summary_dia("Imbalance (XGBoost)", results_imbalance_dia)

4. Applying Models to New Data (apply_dia)

Use a trained model object to make predictions on a new, unseen dataset.

# Apply the trained Bagging model to the test set
bagging_pred_new <- apply_dia(
  trained_model_object = bagging_xb_results$model_object,
  new_data = test_dia,
  label_col_name = "outcome",
  pos_class = "Positive",
  neg_class = "Negative"
)

# Evaluate these new predictions
eval_results_new <- evaluate_model_dia(
  precomputed_prob = bagging_pred_new$score,
  y_data = factor(test_dia$outcome, levels = c(0, 1), labels = c("Positive", "Negative")),
  sample_ids = test_dia$sample,
  threshold_strategy = "default",
  pos_class = "Positive",
  neg_class = "Negative"
)
print(eval_results_new$evaluation_metrics)

5. Visualization (figure_dia)

Generate high-quality plots to evaluate model performance.

# ROC Curve
p1 <- figure_dia(type = "roc", data = results_imbalance_dia)
#plot(p1)

# Precision-Recall Curve
p2 <- figure_dia(type = "prc", data = results_imbalance_dia)
#plot(p2)

# Confusion Matrix
p3 <- figure_dia(type = "matrix", data = results_imbalance_dia)
#plot(p3)

# Stop the parallel cluster
parallel::stopCluster(cl)

E2E documentation built on Aug. 27, 2025, 1:09 a.m.