bone {ElemStatLearn} | R Documentation

## Bone Mineral Density Data

### Description

Measurements in the bone mineral density of 261 north american adolescents, as function of age. Each value is the difference in spnbmd taken on two consecutive visits, divided by the average. The age is the average age over the two visits.

### Usage

    data(bone)

### Format

A data frame with 485 observations on the following 4 variables.

idnum
  identifies the child, and hence the repeat measurements
age
  average of age at two visits
gender
  a factor with levels `female` `male`
spnbmd
  Relative Spinal bone mineral density measurement

### Source

Bachrach LK, Hastie T, Wang M-C, Narasimhan B, Marcus R. Bone Mineral Acquisition in Healthy Asian, Hispanic, Black and Caucasian Youth. A Longitudinal Study. J Clin Endocrinol Metab (1999) 84, 4702-12.

### Examples

    summary(bone)
    # We ignore the repeat measurements:
    # smooth.spline is in standard package stats.
    names(bone)
    # Plot page 128 in the book:
    plot(spnbmd ~ age, data=bone, col =
         ifelse(gender=="male", "blue", "red2"),
         xlab="Age", ylab="Relative Change in Spinal BMD")
    bone.spline.male <- with(subset(bone,gender=="male"),
                    smooth.spline(age, spnbmd,df=12))
    bone.spline.female <- with(subset(bone, gender=="female"),
                    smooth.spline(age, spnbmd, df=12))
    lines(bone.spline.male, col="blue")
    lines(bone.spline.female, col="red2")
    legend(20,0.20, legend=c("male", "Female"), col=c("blue", "red2"),
              lwd=2)

[Package ElemStatLearn version 0.1.1 Index]