Qtools (version 1.0)

mice.impute.rq: QR-based Multiple Imputation

Description

This function is used to multiply impute missing values using quantile regression imputation models.

Usage

mice.impute.rq(y, ry, x, tsf = "none", symm = TRUE,	dbounded = FALSE,
	lambda = NULL, epsilon = 0.001, method.rq = "fn", ...)
mice.impute.rrq(y, ry, x, tsf = "none", symm = TRUE, dbounded = FALSE,
	lambda = NULL, epsilon = 0.001, method.rq = "fn", ...)

Value

A vector of length nmis with imputations.

Details

This function implements the methods proposed by Geraci (2013) to impute missing values using quantile regression models. Uniform values are sampled from [epsilon, 1 - epsilon], therefore allowing the interval to be bounded away from 0 and 1 (default is 0.001). It is possible to specify a quantile regression transformation model with parameter lambda (Geraci and Jones). The function mice.impute.rrq performs imputation based on restricted regression quantiles to avoid quantile crossing (see Geraci 2013 for details).

References

Bottai M, Zhen H. Multiple imputation based on conditional quantile estimation. Epidemiology, Biostatistics and Public Health 2013;10(1):e8758-1. Geraci M. Estimation of regression quantiles in complex surveys with data missing at random: An application to birthweight determinants. Statistical Methods in Medical Research 2013. doi:10.1177/0962280213484401 Geraci M and Jones MC. Improved transformation-based quantile regression. Canadian Journal of Statistics 2015;43(1):118-132. van Buuren S and Groothuis-Oudshoorn K (2011). mice: Multivariate Imputation by Chained Equations in R. Journal of Statistical Software, 45(3), 1-67. URL http://www.jstatsoft.org/v45/i03/.

See Also

ao, tsrq

Examples

# Load package 'mice'
require(mice)

# Load data nhanes
data(nhanes)
nhanes2 <- nhanes
nhanes2$hyp <- as.factor(nhanes2$hyp)

# Impute continuous variables using quantile regression
set.seed(199)
imp <- mice(nhanes2, meth = c("polyreg", "rq", "logreg", "rq"), m = 5)

# estimate linear regression and pool results
fit <- lm.mids(bmi ~ hyp + chl, data = imp)
pool(fit)

# Impute using restricted quantile regression
set.seed(199)
imp <- mice(nhanes2, meth = c("polyreg", "rrq", "logreg", "rrq"), m = 5)
fit <- lm.mids(bmi ~ hyp + chl, data = imp)
pool(fit)

# Impute using quantile regression + Box-Cox transformation with parameter
# lambda = 0 (ie, log transformation)

set.seed(199)
imp <- mice(nhanes2, meth = c("polyreg", "rq", "logreg", "rq"), m = 5, tsf = "bc", lambda = 0)
fit <- lm.mids(bmi ~ hyp + chl, data = imp)
pool(fit)