mice (version 2.2)

boys: Growth of Dutch boys

Description

Height, weight, head circumference and puberty of 748 Dutch boys.

source

Fredriks, A.M,, van Buuren, S., Burgmeijer, R.J., Meulmeester JF, Beuker, R.J., Brugman, E., Roede, M.J., Verloove-Vanhorick, S.P., Wit, J.M. (2000) Continuing positive secular growth change in The Netherlands 1955-1997. Pediatric Research, 47, 316-323. http://www.stefvanbuuren.nl/publications/Continuing secular - Ped Res 2000.pdf

Fredriks, A.M., van Buuren, S., Wit, J.M., Verloove-Vanhorick, S.P. (2000). Body index measurements in 1996-7 compared with 1980. Archives of Disease in Childhood, 82, 107-112. http://www.stefvanbuuren.nl/publications/Body index - ADC 2000.pdf

Details

Random sample of 10% from the cross-sectional data used to construct the Dutch growth references 1997. Variables gen and phb are ordered factors. reg is a factor.

Examples

# create two imputed data sets
imp <- mice(boys, m=1, maxit=2)
z <- complete(imp, 1)

# create imputations for age <8yrs
plot(z$age, z$gen, col=mdc(1:2)[1+is.na(boys$gen)],
 xlab = "Age (years)", ylab = "Tanner Stage Genital")

# figure to show that the default imputation method does not impute BMI
# consistently
plot(z$bmi,z$wgt/(z$hgt/100)^2, col=mdc(1:2)[1+is.na(boys$bmi)],
xlab = "Imputed BMI", ylab="Calculated BMI")

# also, BMI distributions are somewhat different
require(MASS)
oldpar <- par(mfrow=c(1,2))
truehist(z$bmi[!is.na(boys$bmi)],h=1,xlim=c(10,30),ymax=0.25,
col=mdc(1),xlab="BMI observed")
truehist(z$bmi[is.na(boys$bmi)],h=1,xlim=c(10,30),ymax=0.25,
col=mdc(2),xlab="BMI imputed")
par(oldpar)

# repair the inconsistency problem by passive imputation
meth <- imp$meth
meth["bmi"] <- "~I(wgt/(hgt/100)^2)"
pred <- imp$predictorMatrix
pred["hgt","bmi"] <- 0
pred["wgt","bmi"] <- 0
imp2 <- mice(boys, m=1, maxit=2, meth=meth, pred=pred)
z2 <- complete(imp2, 1)

# show that new imputations are consistent
plot(z2$bmi,z2$wgt/(z2$hgt/100)^2, col=mdc(1:2)[1+is.na(boys$bmi)],
ylab="Calculated BMI")

# and compare distributions
oldpar <- par(mfrow=c(1,2))
truehist(z2$bmi[!is.na(boys$bmi)],h=1,xlim=c(10,30),ymax=0.25,col=mdc(1),
xlab="BMI observed")
truehist(z2$bmi[is.na(boys$bmi)],h=1,xlim=c(10,30),ymax=0.25,col=mdc(2),
xlab="BMI imputed")
par(oldpar)