boys: Growth of Dutch boys

In mice: Multivariate Imputation by Chained Equations

Growth of Dutch boys

Description

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

Format

A data frame with 748 rows on the following 9 variables:

age

Decimal age (0-21 years)

hgt

Height (cm)

wgt

Weight (kg)

bmi

Body mass index

hc

Head circumference (cm)

gen

Genital Tanner stage (G1-G5)

phb

Pubic hair (Tanner P1-P6)

tv

Testicular volume (ml)

reg

Region (north, east, west, south, city)

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.

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.

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.

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

mice documentation built on June 7, 2023, 5:38 p.m.