impute_median {simputation}

Impute (group-wise) medians

Description

Impute medians of group-wise medians.

Usage

impute_median(
  dat,
  formula,
  add_residual = c("none", "observed", "normal"),
  type = 7,
  ...
)

Arguments

dat

[data.frame], with variables to be imputed and their predictors.

formula

[formula] imputation model description (See Model description)

add_residual

[character] Type of residual to add. "normal" means that the imputed value is drawn from N(mu,sd) where mu and sd are estimated from the model's residuals (mu should equal zero in most cases). If add_residual = "observed", residuals are drawn (with replacement) from the model's residuals. Ignored for non-numeric predicted variables.

type

[integer] Specifies the algorithm to compute the median. See the 'details' section of quantile.

...

Currently not used.

Model Specification

Formulas are of the form

IMPUTED_VARIABLES ~ MODEL_SPECIFICATION [ | GROUPING_VARIABLES ]

The left-hand-side of the formula object lists the variable or variables to be imputed. Variables in MODEL_SPECIFICATION and/or GROUPING_VARIABLES are used to split the data set into groups prior to imputation. Use ~ 1 to specify that no grouping is to be applied.

Examples

# group-wise median imputation
irisNA <- iris
irisNA[1:3,1] <- irisNA[4:7,2] <- NA
a <- impute_median(irisNA, Sepal.Length ~ Species)
head(a)

# group-wise median imputation, all variables except species

a <- impute_median(irisNA, . - Species ~ Species)
head(a)