20.3 Define some models

• Ensembles are formed from model definitions, which are workflows that contain model recipe & spec (that has been tuned or fit_resample’d).
• The book recommends the racing tuning method.

• You’ll need to save the assessment set predictions and workflow utilized in your tune_grid(), or fit_resamples() objects by setting the control arguments save_pred = TRUE and save_workflow = TRUE.

• If a model has hyperparameters, then you’d be creating multiple candidate models.