This Learner specializes Learner for classification problems:

• task_type is set to "classif".

• Creates Predictions of class PredictionClassif.

• Possible values for predict_types are:

• "response": Predicts a class label for each observation in the test set.

• "prob": Predicts the posterior probability for each class for each observation in the test set.

• "twoclass": The learner works on binary classification problems.

• "multiclass": The learner works on multiclass classification problems.

Predefined learners can be found in the dictionary mlr_learners. Essential classification learners can be found in this dictionary after loading mlr3learners.

## Super class

mlr3::Learner -> LearnerClassif

## Methods

### Public methods

Inherited methods

### Method new()

Creates a new instance of this R6 class.

### Usage

LearnerClassif$new( id, param_set = ParamSet$new(),
predict_types = "response",
feature_types = character(),
properties = character(),
data_formats = "data.table",
packages = character(),
man = NA_character_
)

### Arguments

id

(character(1))
Identifier for the new instance.

param_set

Set of hyperparameters.

predict_types

(character())
Supported predict types. Must be a subset of mlr_reflections$learner_predict_types. feature_types (character()) Feature types the learner operates on. Must be a subset of mlr_reflections$task_feature_types.

properties

(character())
Set of properties of the Learner. Must be a subset of mlr_reflections$learner_properties. The following properties are currently standardized and understood by learners in mlr3: • "missings": The learner can handle missing values in the data. • "weights": The learner supports observation weights. • "importance": The learner supports extraction of importance scores, i.e. comes with an$importance() extractor function (see section on optional extractors in Learner).

• "selected_features": The learner supports extraction of the set of selected features, i.e. comes with a $selected_features() extractor function (see section on optional extractors in Learner). • "oob_error": The learner supports extraction of estimated out of bag error, i.e. comes with a oob_error() extractor function (see section on optional extractors in Learner). data_formats (character()) Set of supported data formats which can be processed during$train() and $predict(), e.g. "data.table". packages (character()) Set of required packages. A warning is signaled by the constructor if at least one of the packages is not installed, but loaded (not attached) later on-demand via requireNamespace(). man (character(1)) String in the format [pkg]::[topic] pointing to a manual page for this object. The referenced help package can be opened via method$help().

### Method clone()

The objects of this class are cloneable with this method.

LearnerClassif$clone(deep = FALSE) ### Arguments deep Whether to make a deep clone. ## Examples # get all classification learners from mlr_learners: lrns = mlr_learners$mget(mlr_learners$keys("^classif")) names(lrns) #> [1] "classif.debug" "classif.featureless" "classif.rpart" # get a specific learner from mlr_learners: lrn = lrn("classif.rpart") print(lrn) #> <LearnerClassifRpart:classif.rpart> #> * Model: - #> * Parameters: xval=0 #> * Packages: rpart #> * Predict Type: response #> * Feature types: logical, integer, numeric, factor, ordered #> * Properties: importance, missings, multiclass, selected_features, #> twoclass, weights # train the learner: task = tsk("iris") lrn$train(task, 1:120) # predict on new observations: lrn$predict(task, 121:150)$confusion
#> truth #> response setosa versicolor virginica #> setosa 0 0 0 #> versicolor 0 0 5 #> virginica 0 0 25