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Function to conduct nested resampling.

Usage

fselect_nested(
  fselector,
  task,
  learner,
  inner_resampling,
  outer_resampling,
  measure = NULL,
  term_evals = NULL,
  term_time = NULL,
  terminator = NULL,
  store_fselect_instance = TRUE,
  store_benchmark_result = TRUE,
  store_models = FALSE,
  check_values = FALSE,
  callbacks = NULL,
  ties_method = "least_features"
)

Arguments

fselector

(FSelector)
Optimization algorithm.

task

(mlr3::Task)
Task to operate on.

learner

(mlr3::Learner)
Learner to optimize the feature subset for.

inner_resampling

(mlr3::Resampling)
Resampling used for the inner loop.

outer_resampling

mlr3::Resampling)
Resampling used for the outer loop.

measure

(mlr3::Measure)
Measure to optimize. If NULL, default measure is used.

term_evals

(integer(1))
Number of allowed evaluations. Ignored if terminator is passed.

term_time

(integer(1))
Maximum allowed time in seconds. Ignored if terminator is passed.

terminator

(Terminator)
Stop criterion of the feature selection.

store_fselect_instance

(logical(1))
If TRUE (default), stores the internally created FSelectInstanceBatchSingleCrit with all intermediate results in slot $fselect_instance. Is set to TRUE, if store_models = TRUE

store_benchmark_result

(logical(1))
Store benchmark result in archive?

store_models

(logical(1)). Store models in benchmark result?

check_values

(logical(1))
Check the parameters before the evaluation and the results for validity?

callbacks

(list of CallbackBatchFSelect)
List of callbacks.

ties_method

(character(1))
The method to break ties when selecting sets while optimizing and when selecting the best set. Can be "least_features" or "random". The option "least_features" (default) selects the feature set with the least features. If there are multiple best feature sets with the same number of features, one is selected randomly. The random method returns a random feature set from the best feature sets. Ignored if multiple measures are used.

Examples

# Nested resampling on Palmer Penguins data set
rr = fselect_nested(
  fselector = fs("random_search"),
  task = tsk("penguins"),
  learner = lrn("classif.rpart"),
  inner_resampling = rsmp ("holdout"),
  outer_resampling = rsmp("cv", folds = 2),
  measure = msr("classif.ce"),
  term_evals = 4)

# Performance scores estimated on the outer resampling
rr$score()
#>     task_id              learner_id resampling_id iteration classif.ce
#>      <char>                  <char>        <char>     <int>      <num>
#> 1: penguins classif.rpart.fselector            cv         1 0.11046512
#> 2: penguins classif.rpart.fselector            cv         2 0.05232558
#> Hidden columns: task, learner, resampling, prediction

# Unbiased performance of the final model trained on the full data set
rr$aggregate()
#> classif.ce 
#> 0.08139535