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Feature selection using Random Search Algorithm.

Source

Bergstra J, Bengio Y (2012). “Random Search for Hyper-Parameter Optimization.” Journal of Machine Learning Research, 13(10), 281--305. https://jmlr.csail.mit.edu/papers/v13/bergstra12a.html.

Details

The feature sets are randomly drawn. The sets are evaluated in batches of size batch_size. Larger batches mean we can parallelize more, smaller batches imply a more fine-grained checking of termination criteria.

Dictionary

This FSelector can be instantiated with the associated sugar function fs():

fs("random_search")

Control Parameters

max_features

integer(1)
Maximum number of features. By default, number of features in mlr3::Task.

batch_size

integer(1)
Maximum number of feature sets to try in a batch.

Super classes

mlr3fselect::FSelector -> mlr3fselect::FSelectorBatch -> FSelectorBatchRandomSearch

Methods

Inherited methods


Method new()

Creates a new instance of this R6 class.


Method clone()

The objects of this class are cloneable with this method.

Usage

FSelectorBatchRandomSearch$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

# Feature Selection
# \donttest{

# retrieve task and load learner
task = tsk("penguins")
learner = lrn("classif.rpart")

# run feature selection on the Palmer Penguins data set
instance = fselect(
  fselector = fs("random_search"),
  task = task,
  learner = learner,
  resampling = rsmp("holdout"),
  measure = msr("classif.ce"),
  term_evals = 10
)

# best performing feature subset
instance$result
#>    bill_depth bill_length body_mass flipper_length island    sex   year
#>        <lgcl>      <lgcl>    <lgcl>         <lgcl> <lgcl> <lgcl> <lgcl>
#> 1:      FALSE        TRUE     FALSE           TRUE  FALSE  FALSE  FALSE
#>                      features n_features classif.ce
#>                        <list>      <int>      <num>
#> 1: bill_length,flipper_length          2 0.04347826

# all evaluated feature subsets
as.data.table(instance$archive)
#>     bill_depth bill_length body_mass flipper_length island    sex   year
#>         <lgcl>      <lgcl>    <lgcl>         <lgcl> <lgcl> <lgcl> <lgcl>
#>  1:      FALSE       FALSE     FALSE           TRUE   TRUE  FALSE   TRUE
#>  2:      FALSE       FALSE      TRUE           TRUE   TRUE  FALSE   TRUE
#>  3:       TRUE       FALSE     FALSE           TRUE  FALSE   TRUE  FALSE
#>  4:      FALSE        TRUE     FALSE           TRUE   TRUE   TRUE   TRUE
#>  5:       TRUE       FALSE     FALSE           TRUE   TRUE   TRUE  FALSE
#>  6:       TRUE       FALSE     FALSE           TRUE   TRUE   TRUE  FALSE
#>  7:      FALSE       FALSE      TRUE           TRUE   TRUE  FALSE  FALSE
#>  8:      FALSE        TRUE     FALSE           TRUE  FALSE  FALSE  FALSE
#>  9:       TRUE        TRUE     FALSE          FALSE  FALSE  FALSE   TRUE
#> 10:      FALSE       FALSE      TRUE          FALSE  FALSE  FALSE   TRUE
#>     classif.ce runtime_learners           timestamp batch_nr warnings errors
#>          <num>            <num>              <POSc>    <int>    <int>  <int>
#>  1: 0.18260870            0.009 2024-05-13 08:21:51        1        0      0
#>  2: 0.18260870            0.009 2024-05-13 08:21:51        1        0      0
#>  3: 0.31304348            0.009 2024-05-13 08:21:51        1        0      0
#>  4: 0.04347826            0.009 2024-05-13 08:21:51        1        0      0
#>  5: 0.17391304            0.014 2024-05-13 08:21:51        1        0      0
#>  6: 0.17391304            0.013 2024-05-13 08:21:51        1        0      0
#>  7: 0.18260870            0.010 2024-05-13 08:21:51        1        0      0
#>  8: 0.04347826            0.009 2024-05-13 08:21:51        1        0      0
#>  9: 0.13043478            0.009 2024-05-13 08:21:51        1        0      0
#> 10: 0.42608696            0.009 2024-05-13 08:21:51        1        0      0
#>                                       features n_features  resample_result
#>                                         <list>     <list>           <list>
#>  1:                 flipper_length,island,year          3 <ResampleResult>
#>  2:       body_mass,flipper_length,island,year          4 <ResampleResult>
#>  3:              bill_depth,flipper_length,sex          3 <ResampleResult>
#>  4: bill_length,flipper_length,island,sex,year          5 <ResampleResult>
#>  5:       bill_depth,flipper_length,island,sex          4 <ResampleResult>
#>  6:       bill_depth,flipper_length,island,sex          4 <ResampleResult>
#>  7:            body_mass,flipper_length,island          3 <ResampleResult>
#>  8:                 bill_length,flipper_length          2 <ResampleResult>
#>  9:                bill_depth,bill_length,year          3 <ResampleResult>
#> 10:                             body_mass,year          2 <ResampleResult>

# subset the task and fit the final model
task$select(instance$result_feature_set)
learner$train(task)
# }