irmi: Iterative robust model-based imputation (IRMI)

In VIM: Visualization and Imputation of Missing Values

Iterative robust model-based imputation (IRMI)

Description

In each step of the iteration, one variable is used as a response variable and the remaining variables serve as the regressors.

Usage

irmi(
  x,
  eps = 5,
  maxit = 100,
  mixed = NULL,
  mixed.constant = NULL,
  count = NULL,
  step = FALSE,
  robust = FALSE,
  takeAll = TRUE,
  noise = TRUE,
  noise.factor = 1,
  force = FALSE,
  robMethod = "MM",
  force.mixed = TRUE,
  mi = 1,
  addMixedFactors = FALSE,
  trace = FALSE,
  init.method = "kNN",
  modelFormulas = NULL,
  multinom.method = "multinom",
  imp_var = TRUE,
  imp_suffix = "imp"
)

Arguments

x	data.frame or matrix
eps	threshold for convergency
maxit	maximum number of iterations
mixed	column index of the semi-continuous variables
mixed.constant	vector with length equal to the number of semi-continuous variables specifying the point of the semi-continuous distribution with non-zero probability
count	column index of count variables
step	a stepwise model selection is applied when the parameter is set to TRUE
robust	if TRUE, robust regression methods will be applied
takeAll	takes information of (initialised) missings in the response as well for regression imputation.
noise	irmi has the option to add a random error term to the imputed values, this creates the possibility for multiple imputation. The error term has mean 0 and variance corresponding to the variance of the regression residuals.
noise.factor	amount of noise.
force	if TRUE, the algorithm tries to find a solution in any case, possible by using different robust methods automatically.
robMethod	regression method when the response is continuous.
force.mixed	if TRUE, the algorithm tries to find a solution in any case, possible by using different robust methods automatically.
mi	number of multiple imputations.
addMixedFactors	if TRUE add additional factor variable for each mixed variable as X variable in the regression
trace	Additional information about the iterations when trace equals TRUE.
init.method	Method for initialization of missing values (kNN or median)
modelFormulas	a named list with the name of variables for the rhs of the formulas, which must contain a rhs formula for each variable with missing values, it should look like 'list(y1=c("x1","x2"),y2=c("x1","x3"))“ if factor variables for the mixed variables should be created for the regression models
multinom.method	Method for estimating the multinomial models (current default and only available method is multinom)
imp_var	TRUE/FALSE if a TRUE/FALSE variables for each imputed variable should be created show the imputation status
imp_suffix	suffix for the TRUE/FALSE variables showing the imputation status

Details

The method works sequentially and iterative. The method can deal with a mixture of continuous, semi-continuous, ordinal and nominal variables including outliers.

A full description of the method can be found in the mentioned reference.

Value

the imputed data set.

Author(s)

Matthias Templ, Alexander Kowarik

References

M. Templ, A. Kowarik, P. Filzmoser (2011) Iterative stepwise regression imputation using standard and robust methods. Journal of Computational Statistics and Data Analysis, Vol. 55, pp. 2793-2806.

A. Kowarik, M. Templ (2016) Imputation with R package VIM. Journal of Statistical Software, 74(7), 1-16.

See Also

mi::mi()

Other imputation methods: hotdeck(), impPCA(), kNN(), matchImpute(), medianSamp(), rangerImpute(), regressionImp(), sampleCat()

Examples

data(sleep)
irmi(sleep)

data(testdata)
imp_testdata1 <- irmi(testdata$wna, mixed = testdata$mixed)

# mixed.constant != 0 (-10)
testdata$wna$m1[testdata$wna$m1 == 0] <- -10
testdata$wna$m2 <- log(testdata$wna$m2 + 0.001)
imp_testdata2 <- irmi(
  testdata$wna,
  mixed = testdata$mixed,
  mixed.constant = c(-10,log(0.001))
)
imp_testdata2$m2 <- exp(imp_testdata2$m2) - 0.001

#example with fixed formulas for the variables with missing
form = list(
  NonD  = c("BodyWgt", "BrainWgt"),
  Dream = c("BodyWgt", "BrainWgt"),
  Sleep = c("BrainWgt"           ),
  Span  = c("BodyWgt"            ),
  Gest  = c("BodyWgt", "BrainWgt")
)
irmi(sleep, modelFormulas = form, trace = TRUE)

# Example with ordered variable
td <- testdata$wna
td$c1 <- as.ordered(td$c1)
irmi(td)

VIM documentation built on Aug. 25, 2022, 5:07 p.m.