callback_batch_fselect: Create Feature Selection Callback

In mlr3fselect: Feature Selection for 'mlr3'

Create Feature Selection Callback

Description

Function to create a CallbackBatchFSelect. Predefined callbacks are stored in the dictionary mlr_callbacks and can be retrieved with clbk().

Feature selection callbacks can be called from different stages of feature selection. The stages are prefixed with ⁠on_*⁠. The ⁠on_auto_fselector_*⁠ stages are only available when the callback is used in an AutoFSelector.

Start Automatic Feature Selection
  Start Feature Selection
      - on_optimization_begin
      Start FSelect Batch
          - on_optimizer_before_eval
          Start Evaluation
              - on_eval_after_design
              - on_eval_after_benchmark
              - on_eval_before_archive
          End Evaluation
          - on_optimizer_after_eval
      End FSelect Batch
      - on_result
      - on_optimization_end
  End Feature Selection
  - on_auto_fselector_before_final_model
  - on_auto_fselector_after_final_model
End Automatic Feature Selection

See also the section on parameters for more information on the stages. A feature selection callback works with bbotk::ContextBatch and ContextBatchFSelect.

Usage

callback_batch_fselect(
  id,
  label = NA_character_,
  man = NA_character_,
  on_optimization_begin = NULL,
  on_optimizer_before_eval = NULL,
  on_eval_after_design = NULL,
  on_eval_after_benchmark = NULL,
  on_eval_before_archive = NULL,
  on_optimizer_after_eval = NULL,
  on_result = NULL,
  on_optimization_end = NULL,
  on_auto_fselector_before_final_model = NULL,
  on_auto_fselector_after_final_model = NULL
)

Arguments

id	(character(1)) Identifier for the new instance.
label	(character(1)) Label for the new instance.
man	(character(1)) String in the format ⁠[pkg]::[topic]⁠ pointing to a manual page for this object. The referenced help package can be opened via method ⁠$help()⁠.
on_optimization_begin	(⁠function()⁠) Stage called at the beginning of the optimization. Called in Optimizer$optimize().
on_optimizer_before_eval	(⁠function()⁠) Stage called after the optimizer proposes points. Called in OptimInstance$eval_batch().
on_eval_after_design	(⁠function()⁠) Stage called after design is created. Called in ObjectiveFSelectBatch$eval_many().
on_eval_after_benchmark	(⁠function()⁠) Stage called after feature sets are evaluated. Called in ObjectiveFSelectBatch$eval_many().
on_eval_before_archive	(⁠function()⁠) Stage called before performance values are written to the archive. Called in ObjectiveFSelectBatch$eval_many().
on_optimizer_after_eval	(⁠function()⁠) Stage called after points are evaluated. Called in OptimInstance$eval_batch().
on_result	(⁠function()⁠) Stage called after result are written. Called in OptimInstance$assign_result().
on_optimization_end	(⁠function()⁠) Stage called at the end of the optimization. Called in Optimizer$optimize().
on_auto_fselector_before_final_model	(⁠function()⁠) Stage called before the final model is trained. Called in AutoFSelector$train().
on_auto_fselector_after_final_model	(⁠function()⁠) Stage called after the final model is trained. Called in AutoFSelector$train().

Details

When implementing a callback, each function must have two arguments named callback and context. A callback can write data to the state (⁠$state⁠), e.g. settings that affect the callback itself. Avoid writing large data the state.

Examples

# Write archive to disk
callback_batch_fselect("mlr3fselect.backup",
  on_optimization_end = function(callback, context) {
    saveRDS(context$instance$archive, "archive.rds")
  }
)

mlr3fselect documentation built on Aug. 8, 2025, 7:46 p.m.