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#' @title k-Nearest-Neighbor Regression Learner
#'
#' @name mlr_learners_regr.kknn
#'
#' @description
#' k-Nearest-Neighbor regression.
#' Calls [kknn::kknn()] from package \CRANpkg{kknn}.
#'
#' @section Initial parameter values:
#' - `store_model`:
#' - See note.
#'
#' @template note_kknn
#'
#' @templateVar id regr.kknn
#' @template learner
#'
#' @references
#' `r format_bib("hechenbichler_2004", "samworth_2012", "cover_1967")`
#'
#' @export
#' @template seealso_learner
#' @template example
LearnerRegrKKNN = R6Class("LearnerRegrKKNN",
inherit = LearnerRegr,
public = list(
#' @description
#' Creates a new instance of this [R6][R6::R6Class] class.
initialize = function() {
ps = ps(
k = p_int(default = 7L, lower = 1L, tags = "train"),
distance = p_dbl(0, default = 2, tags = "train"),
kernel = p_fct(c("rectangular", "triangular", "epanechnikov", "biweight", "triweight", "cos", "inv", "gaussian", "rank", "optimal"), default = "optimal", tags = "train"),
scale = p_lgl(default = TRUE, tags = "train"),
ykernel = p_uty(default = NULL, tags = "train"),
store_model = p_lgl(default = FALSE, tags = "train")
)
ps$values = list(k = 7L)
super$initialize(
id = "regr.kknn",
param_set = ps,
feature_types = c("logical", "integer", "numeric", "factor", "ordered"),
packages = c("mlr3learners", "kknn"),
label = "k-Nearest-Neighbor",
man = "mlr3learners::mlr_learners_regr.kknn"
)
}
),
private = list(
.train = function(task) {
# https://github.com/mlr-org/mlr3learners/issues/191
pv = self$param_set$get_values(tags = "train")
if (pv$k >= task$nrow) {
stopf("Parameter k = %i must be smaller than the number of observations n = %i",
pv$k, task$nrow)
}
list(
formula = task$formula(),
data = task$data(),
pv = pv,
kknn = NULL
)
},
.predict = function(task) {
model = self$model
newdata = ordered_features(task, self)
pv = insert_named(model$pv, self$param_set$get_values(tags = "predict"))
with_package("kknn", { # https://github.com/KlausVigo/kknn/issues/16
p = invoke(kknn::kknn,
formula = model$formula, train = model$data,
test = newdata, .args = remove_named(pv, "store_model"))
})
if (isTRUE(pv$store_model)) {
self$state$model$kknn = p
}
list(response = p$fitted.values)
}
)
)
#' @include aaa.R
learners[["regr.kknn"]] = LearnerRegrKKNN
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