Recursive Forecast Learner — RecursiveForecaster • mlr3forecast

A mlr3::Learner for iterative one-step-ahead forecasting. Wraps a mlr3pipelines::GraphLearner (held internally, mirroring DirectForecaster and mlr3tuning::AutoTuner). Training is fully delegated to the graph. At predict time the forecaster builds a combined task (training history + test rows with NA targets) backed by a single mutable data.table::data.table(), iterates through the test rows in (key, order) order, and writes each prediction back into the combined task's target column so that lag and rolling features for the next step reflect the freshly predicted value.

Can be constructed in two ways:

Simple: RecursiveForecaster$new(learner, lags = 1:3) – internally builds po("fcst.lags", lags = lags) %>>% learner.
Graph: RecursiveForecaster$new(graph) – takes an arbitrary mlr3pipelines::Graph or mlr3pipelines::PipeOp.

Target transformations

A target transformation (e.g. mlr_pipeops_fcst.targetdiff, mlr3pipelines::PipeOpTargetMutate) must wrap the forecaster, not be placed inside its graph. Wrap it with mlr3pipelines::ppl("targettrafo") so the whole series is transformed once up front, the recursion runs entirely on the transformed scale, and predictions are inverted once at the end:

flrn = as_learner(ppl("targettrafo",
  graph = RecursiveForecaster$new(lrn("regr.rpart"), lags = 1:12),
  trafo_pipeop = po("fcst.targetdiff", lag = 1L)
))
flrn$train(task, split$train)
flrn$predict(task, split$test)  # predictions are on the original scale

Placing a mlr3pipelines::PipeOpTargetTrafo inside the graph is not supported and is rejected at construction: it would entangle the transformation with the iterative lag/rolling feedback, which read the original-scale backend, producing a train/predict scale mismatch.

Super class

mlr3::Learner -> RecursiveForecaster

Active bindings

learner: (mlr3::Learner)
The base regression learner.
lags: (integer() | NULL)
The lags used, or NULL if no PipeOpFcstLags is in the graph.
param_set: (paradox::ParamSet)
Set of hyperparameters.
marshaled: (logical(1))
Whether the learner's model is currently in marshaled form.
predict_type: (character(1))
Stores the currently active predict type.

Methods

Inherited methods

`RecursiveForecaster$new()`

Creates a new instance of this R6 class.

Usage

RecursiveForecaster$new(
  learner,
  lags = NULL,
  id = NULL,
  param_vals = list(),
  predict_type = NULL,
  clone_graph = TRUE
)

Arguments

learner: (mlr3::Learner | mlr3pipelines::Graph | mlr3pipelines::PipeOp)
A regression learner (when lags is provided) or a graph/PipeOp.
lags: (integer() | NULL)
The lag values to use for creating lag features. If provided, learner is wrapped with po("fcst.lags", lags = lags). If NULL, learner must be a mlr3pipelines::Graph or mlr3pipelines::PipeOp.
id: (character(1) | NULL)
Identifier, default NULL (auto-generated).
param_vals: (named list())
List of hyperparameter settings.
predict_type: (character(1) | NULL)
The predict type, default NULL.
clone_graph: (logical(1))
Whether to clone the graph, default TRUE.

`RecursiveForecaster$print()`

Printer.

Usage

RecursiveForecaster$print(...)

Arguments

...: (ignored).

`RecursiveForecaster$marshal()`

Marshal the learner's model.

Usage

RecursiveForecaster$marshal(...)

Arguments

...: (any)
Additional arguments passed to mlr3::marshal_model().

`RecursiveForecaster$unmarshal()`

Unmarshal the learner's model.

Usage

RecursiveForecaster$unmarshal(...)

Arguments

...: (any)
Additional arguments passed to mlr3::unmarshal_model().

`RecursiveForecaster$clone()`

The objects of this class are cloneable with this method.

Usage

RecursiveForecaster$clone(deep = FALSE)

Arguments

deep: Whether to make a deep clone.

Examples

library(mlr3pipelines)

task = tsk("airpassengers")
flrn = RecursiveForecaster$new(lrn("regr.rpart"), lags = 1:3)
split = partition(task, ratio = 0.8)
flrn$train(task, split$train)
flrn$predict(task, split$test)
#> 
#> ── <PredictionRegr> for 29 observations: ───────────────────────────────────────
#>  row_ids truth response      month
#>      116   505 391.9375 1958-08-01
#>      117   404 391.9375 1958-09-01
#>      118   359 391.9375 1958-10-01
#>      ---   ---      ---        ---
#>      142   461 391.9375 1960-10-01
#>      143   390 391.9375 1960-11-01
#>      144   432 391.9375 1960-12-01

# graph: custom preprocessing pipeline
graph = po("fcst.lags", lags = 1:3) %>>% lrn("regr.rpart")
flrn = RecursiveForecaster$new(graph)
flrn$train(task, split$train)
flrn$predict(task, split$test)
#> 
#> ── <PredictionRegr> for 29 observations: ───────────────────────────────────────
#>  row_ids truth response      month
#>      116   505 391.9375 1958-08-01
#>      117   404 391.9375 1958-09-01
#>      118   359 391.9375 1958-10-01
#>      ---   ---      ---        ---
#>      142   461 391.9375 1960-10-01
#>      143   390 391.9375 1960-11-01
#>      144   432 391.9375 1960-12-01