Stai prevedendo correttamente?

Il tuo modello dovrebbe essere il più efficace possibile, giusto? Un modo per valutarlo è contare quante volte ha previsto le classi corrette rispetto al numero totale di previsioni effettuate. Come spiegato nel video, questa misura di performance si chiama accuracy. Puoi calcolarla manualmente oppure usare una scorciatoia comoda: entrambi i metodi portano allo stesso risultato.

Sono già caricati la matrice di confusione diabetes_matrix e il tibble predictions_combined.

Questo esercizio fa parte del corso

Machine Learning con modelli ad albero in R

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Esercizio pratico interattivo

Prova a risolvere questo esercizio completando il codice di esempio.

# Calculate the number of correctly predicted classes
correct_predictions <- 75 + ___

# Calculate the number of all predicted classes
all_predictions <- ___ + ___ + 18 + ___

# Calculate and print the accuracy
acc_manual <- ___ / ___
___

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Questo esercizio fa parte del corso

Machine Learning con modelli ad albero in R

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Ready to build a real machine learning pipeline? Complete step-by-step exercises to learn how to create decision trees, split your data, and predict which patients are most likely to suffer from diabetes. Last but not least, you’ll build performance measures to assess your models and judge your predictions.

Exercise 1: Benvenuto al corso!Exercise 2: Perché metodi basati su alberi?Exercise 3: Specifica quell'albero Exercise 4: Allena quel modello Exercise 5: Come far crescere il tuo albero Exercise 6: Suddivisione train/test Exercise 7: Evitare lo sbilanciamento delle classi Exercise 8: Da zero a eroe Exercise 9: Predici e valuta Exercise 10: Fai delle predizioni Exercise 11: Decifra la matrice Exercise 12: Stai prevedendo correttamente?

Esercizio in corso

Ready for some candy? Use a chocolate rating dataset to build regression trees and assess their performance using suitable error measures. You’ll overcome statistical insecurities of single train/test splits by applying sweet techniques like cross-validation and then dive even deeper by mastering the bias-variance tradeoff.

Exercise 1: Continuous outcomes Exercise 2: Train a regression tree Exercise 3: Predict new values Exercise 4: Inspect model output Exercise 5: Performance metrics for regression trees Exercise 6: In-sample performance Exercise 7: Out-of-sample performance Exercise 8: Bigger mistakes, bigger penalty Exercise 9: Cross-validation Exercise 10: Create the folds Exercise 11: Fit the folds Exercise 12: Evaluate the folds Exercise 13: Bias-variance tradeoff Exercise 14: Call things by their names Exercise 15: Adjust model complexity Exercise 16: In-sample and out-of-sample performance

Time to get serious with tuning your hyperparameters and interpreting receiver operating characteristic (ROC) curves. In this chapter, you’ll leverage the wisdom of the crowd with ensemble models like bagging or random forests and build ensembles that forecast which credit card customers are most likely to churn.

Exercise 1: Tuning hyperparameters Exercise 2: Generate a tuning grid Exercise 3: Tune along the grid Exercise 4: Pick the winner Exercise 5: More model measures Exercise 6: Calculate specificity Exercise 7: Draw the ROC curve Exercise 8: Area under the ROC curve Exercise 9: Bagged trees Exercise 10: Create bagged trees Exercise 11: In-sample ROC and AUC Exercise 12: Check for overfitting Exercise 13: Random forest Exercise 14: Bagged trees vs. random forest Exercise 15: Variable importance

Ready for the high society of tree-based models? Apply gradient boosting to create powerful ensembles that perform better than anything that you have seen or built. Learn about their fine-tuning and how to compare different models to pick a winner for production.

Exercise 1: Introduction to boosting Exercise 2: Bagging vs. boosting Exercise 3: Specify a boosted ensemble Exercise 4: Gradient boosting Exercise 5: Train a boosted ensemble Exercise 6: Evaluate the ensemble Exercise 7: Compare to a single classifier Exercise 8: Optimize the boosted ensemble Exercise 9: Tuning preparation Exercise 10: The actual tuning Exercise 11: Finalize the model Exercise 12: Model comparison Exercise 13: Compare AUC Exercise 14: Plot ROC curves Exercise 15: Wrap-up