Perform alternative path branching: PipeOpBranch has multiple output channels that connect to different paths in a Graph. At any time, only one of these paths will be taken for execution. At the end of the different paths, the PipeOpUnbranch PipeOp must be used to indicate the end of alternative paths.

Not to be confused with PipeOpCopy, the naming scheme is a bit unfortunate.

## Format

R6Class object inheriting from PipeOp.

## Parameters

• selection :: numeric(1) | character(1)
Selection of branching path to take. Is a ParamInt if the options parameter during construction was a numeric(1), and ranges from 1 to options. Is a ParamFct if the options parameter was a character and its possible values are the options values. Initialized to either 1 (if the options construction argument is numeric(1)) or the first element of options (if it is character).

## Internals

Alternative path branching is handled by the PipeOp backend. To indicate that a path should not be taken, PipeOpBranch returns the NO_OP object on its output channel. The PipeOp handles each NO_OP input by automatically returning a NO_OP output without calling private$.train() or private$.predict(), until PipeOpUnbranch is reached. PipeOpUnbranch will then take multiple inputs, all except one of which must be a NO_OP, and forward the only non-NO_OP object on its output.

## Fields

Only fields inherited from PipeOp.

## Methods

Only methods inherited from PipeOp.

library("mlr3") pca = po("pca") nop = po("nop") choices = c("pca", "nothing") gr = po("branch", choices) %>>% gunion(list(pca, nop)) %>>% po("unbranch", choices) gr$param_set$values$branch.selection = "pca" gr$train(tsk("iris"))
#> $unbranch.output #> <TaskClassif:iris> (150 x 5) #> * Target: Species #> * Properties: multiclass #> * Features (4): #> - dbl (4): PC1, PC2, PC3, PC4 #> gr$param_set$values$branch.selection = "nothing" gr$train(tsk("iris")) #>$unbranch.output #> <TaskClassif:iris> (150 x 5) #> * Target: Species #> * Properties: multiclass #> * Features (4): #> - dbl (4): Petal.Length, Petal.Width, Sepal.Length, Sepal.Width #>