boys | R Documentation |

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

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)

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.

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.

```
# 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)
```

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