recipes: step_impute_median – R documentation

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step_impute_median

Impute Numeric Data Using the Median

Description

step_impute_median creates a specification of a recipe step that will substitute missing values of numeric variables by the training set median of those variables.

Usage

step_impute_median(
  recipe,
  ...,
  role = NA,
  trained = FALSE,
  medians = NULL,
  skip = FALSE,
  id = rand_id("impute_median")
)

step_medianimpute(
  recipe,
  ...,
  role = NA,
  trained = FALSE,
  medians = NULL,
  skip = FALSE,
  id = rand_id("impute_median")
)

## S3 method for class 'step_impute_median'
tidy(x, ...)

Arguments

`recipe`	A recipe object. The step will be added to the sequence of operations for this recipe.
`...`	One or more selector functions to choose which variables are affected by the step. See `selections()` for more details. For the `tidy` method, these are not currently used.
`role`	Not used by this step since no new variables are created.
`trained`	A logical to indicate if the quantities for preprocessing have been estimated.
`medians`	A named numeric vector of medians. This is `NULL` until computed by `prep.recipe()`. Note that, if the original data are integers, the median will be converted to an integer to maintain the same data type.
`skip`	A logical. Should the step be skipped when the recipe is baked by `bake.recipe()`? While all operations are baked when `prep.recipe()` is run, some operations may not be able to be conducted on new data (e.g. processing the outcome variable(s)). Care should be taken when using `skip = TRUE` as it may affect the computations for subsequent operations
`id`	A character string that is unique to this step to identify it.
`x`	A `step_impute_median` object.

Details

step_impute_median estimates the variable medians from the data used in the training argument of prep.recipe. bake.recipe then applies the new values to new data sets using these medians.

As of recipes 0.1.16, this function name changed from step_medianimpute() to step_impute_median().

Value

An updated version of recipe with the new step added to the sequence of existing steps (if any). For the tidy method, a tibble with columns terms (the selectors or variables selected) and model (the median value).

Examples

library(modeldata)
data("credit_data")

## missing data per column
vapply(credit_data, function(x) mean(is.na(x)), c(num = 0))

set.seed(342)
in_training <- sample(1:nrow(credit_data), 2000)

credit_tr <- credit_data[ in_training, ]
credit_te <- credit_data[-in_training, ]
missing_examples <- c(14, 394, 565)

rec <- recipe(Price ~ ., data = credit_tr)

impute_rec <- rec %>%
  step_impute_median(Income, Assets, Debt)

imp_models <- prep(impute_rec, training = credit_tr)

imputed_te <- bake(imp_models, new_data = credit_te, everything())

credit_te[missing_examples,]
imputed_te[missing_examples, names(credit_te)]

tidy(impute_rec, number = 1)
tidy(imp_models, number = 1)

recipes

Preprocessing Tools to Create Design Matrices

v0.1.16

MIT + file LICENSE

Authors

Max Kuhn [aut, cre], Hadley Wickham [aut], RStudio [cph]

Initial release