Generates a more balanced data set by creating synthetic instances of the minority class using the SMOTE algorithm. The algorithm samples for each minority instance a new data point based on the K nearest neighbors of that data point. It can only be applied to tasks with numeric features. See smotefamily::SMOTE for details.

Format

R6Class object inheriting from PipeOpTaskPreproc/PipeOp.

Construction

PipeOpSmote$new(id = "smote", param_vals = list())

Identifier of resulting object, default "smote".

  • param_vals :: named list
    List of hyperparameter settings, overwriting the hyperparameter settings that would otherwise be set during construction. Default list().

Input and Output Channels

Input and output channels are inherited from PipeOpTaskPreproc.

The output during training is the input Task with added synthetic rows for the minority class. The output during prediction is the unchanged input.

State

The $state is a named list with the $state elements inherited from PipeOpTaskPreproc.

Parameters

The parameters are the parameters inherited from PipeOpTaskPreproc, as well as:

  • K :: numeric(1)
    The number of nearest neighbors used for sampling new values. See SMOTE().

  • dup_size :: numeric
    Desired times of synthetic minority instances over the original number of majority instances. See SMOTE().

Internals

For details see:
Chawla, N., Bowyer, K., Hall, L. and Kegelmeyer, W. 2002.
SMOTE: Synthetic minority oversampling technique.
Journal of Artificial Intelligence Research. 16, 321-357.

Fields

Only fields inherited from PipeOpTaskPreproc/PipeOp.

Methods

Only methods inherited from PipeOpTaskPreproc/PipeOp.

See also

Examples

library("mlr3") # Create example task data_example = smotefamily::sample_generator(1000, ratio = 0.80) task = TaskClassif$new(id = "example", backend = data_example, target = "result") task$data()
#> result X1 X2 #> 1: n 0.2866815 0.45899585 #> 2: n 0.2682259 0.20055563 #> 3: n 0.8959587 0.28225572 #> 4: p 0.5282639 0.33736117 #> 5: n 0.9983724 0.13857375 #> --- #> 996: n 0.2099023 0.88892125 #> 997: p 0.6939768 0.49183863 #> 998: n 0.9204687 0.05490594 #> 999: n 0.8816077 0.30730362 #> 1000: n 0.8660524 0.59036143
table(task$data()$result)
#> #> n p #> 768 232
# Generate synthetic data for minority class pop = po("smote") smotedata = pop$train(list(task))[[1]]$data() table(smotedata$result)
#> #> n p #> 768 696