mlr_pipeops_classweights | R Documentation |
Adds a class weight column to the Task
that different Learner
s may be
able to use for sample weighting. Sample weights are added to each sample according to the target class.
Only binary classification tasks are supported.
Caution: when constructed naively without parameter, the weights are all set to 1. The minor_weight
parameter
must be adjusted for this PipeOp
to be useful.
Note this only sets the "weights_learner"
column.
It therefore influences the behaviour of subsequent Learner
s, but does not influence resampling or evaluation metric weights.
R6Class
object inheriting from PipeOpTaskPreproc
/PipeOp
.
PipeOpClassWeights$new(id = "classweights", param_vals = list())
id
:: character(1)
Identifier of the resulting object, default "classweights"
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 are inherited from PipeOpTaskPreproc
. Instead of a Task
, a
TaskClassif
is used as input and output during training and prediction.
The output during training is the input Task
with added weights column according to target class.
The output during prediction is the unchanged input.
The $state
is a named list
with the $state
elements inherited from PipeOpTaskPreproc
.
The parameters are the parameters inherited from PipeOpTaskPreproc
; however, the affect_columns
parameter is not present. Further parameters are:
minor_weight
:: numeric(1)
Weight given to samples of the minor class. Major class samples have weight 1. Initialized to 1.
Introduces, or overwrites, the "weights" column in the Task
. However, the Learner
method needs to
respect weights for this to have an effect.
The newly introduced column is named .WEIGHTS
; there will be a naming conflict if this column already exists and is not a
weight column itself.
Only fields inherited from PipeOpTaskPreproc
/PipeOp
.
Only methods inherited from PipeOpTaskPreproc
/PipeOp
.
https://mlr-org.com/pipeops.html
Other PipeOps:
PipeOp
,
PipeOpEnsemble
,
PipeOpImpute
,
PipeOpTargetTrafo
,
PipeOpTaskPreproc
,
PipeOpTaskPreprocSimple
,
mlr_pipeops
,
mlr_pipeops_adas
,
mlr_pipeops_blsmote
,
mlr_pipeops_boxcox
,
mlr_pipeops_branch
,
mlr_pipeops_chunk
,
mlr_pipeops_classbalancing
,
mlr_pipeops_classifavg
,
mlr_pipeops_colapply
,
mlr_pipeops_collapsefactors
,
mlr_pipeops_colroles
,
mlr_pipeops_copy
,
mlr_pipeops_datefeatures
,
mlr_pipeops_encode
,
mlr_pipeops_encodeimpact
,
mlr_pipeops_encodelmer
,
mlr_pipeops_featureunion
,
mlr_pipeops_filter
,
mlr_pipeops_fixfactors
,
mlr_pipeops_histbin
,
mlr_pipeops_ica
,
mlr_pipeops_imputeconstant
,
mlr_pipeops_imputehist
,
mlr_pipeops_imputelearner
,
mlr_pipeops_imputemean
,
mlr_pipeops_imputemedian
,
mlr_pipeops_imputemode
,
mlr_pipeops_imputeoor
,
mlr_pipeops_imputesample
,
mlr_pipeops_kernelpca
,
mlr_pipeops_learner
,
mlr_pipeops_missind
,
mlr_pipeops_modelmatrix
,
mlr_pipeops_multiplicityexply
,
mlr_pipeops_multiplicityimply
,
mlr_pipeops_mutate
,
mlr_pipeops_nmf
,
mlr_pipeops_nop
,
mlr_pipeops_ovrsplit
,
mlr_pipeops_ovrunite
,
mlr_pipeops_pca
,
mlr_pipeops_proxy
,
mlr_pipeops_quantilebin
,
mlr_pipeops_randomprojection
,
mlr_pipeops_randomresponse
,
mlr_pipeops_regravg
,
mlr_pipeops_removeconstants
,
mlr_pipeops_renamecolumns
,
mlr_pipeops_replicate
,
mlr_pipeops_rowapply
,
mlr_pipeops_scale
,
mlr_pipeops_scalemaxabs
,
mlr_pipeops_scalerange
,
mlr_pipeops_select
,
mlr_pipeops_smote
,
mlr_pipeops_smotenc
,
mlr_pipeops_spatialsign
,
mlr_pipeops_subsample
,
mlr_pipeops_targetinvert
,
mlr_pipeops_targetmutate
,
mlr_pipeops_targettrafoscalerange
,
mlr_pipeops_textvectorizer
,
mlr_pipeops_threshold
,
mlr_pipeops_tunethreshold
,
mlr_pipeops_unbranch
,
mlr_pipeops_updatetarget
,
mlr_pipeops_vtreat
,
mlr_pipeops_yeojohnson
library("mlr3")
task = tsk("spam")
opb = po("classweights")
# task weights
if ("weights_learner" %in% names(task)) {
task$weights_learner # recent mlr3-versions
} else {
task$weights # old mlr3-versions
}
# double the instances in the minority class (spam)
opb$param_set$values$minor_weight = 2
result = opb$train(list(task))[[1L]]
if ("weights_learner" %in% names(result)) {
result$weights_learner # recent mlr3-versions
} else {
result$weights # old mlr3-versions
}
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