Orthodont {nlme} | R Documentation

## Growth curve data on an orthdontic measurement

### Description

The `Orthodont` data frame has 108 rows and 4 columns of the change in an orthdontic measurement over time for several young subjects.

### Format

This data frame contains the following columns:

distance
  a numeric vector of distances from the pituitary to the pterygomaxillary fissure (mm). These distances are measured on x-ray images of the skull.
age
  a numeric vector of ages of the subject (yr).
Subject
  an ordered factor indicating the subject on which the measurement was made. The levels are labelled `M01` to `M16` for the males and `F01` to `F13` for the females. The ordering is by increasing average distance within sex.
Sex
  a factor with levels `Male` and `Female`

### Details

Investigators at the University of North Carolina Dental School followed the growth of 27 children (16 males, 11 females) from age 8 until age 14. Every two years they measured the distance between the pituitary and the pterygomaxillary fissure, two points that are easily identified on x-ray exposures of the side of the head.

### Source

Pinheiro, J. C. and Bates, D. M. (2000), Mixed-Effects Models in S and S-PLUS, Springer, New York. (Appendix A.17)

Potthoff, R. F. and Roy, S. N. (1964), ``A generalized multivariate analysis of variance model useful especially for growth curve problems'', Biometrika, 51, 313–326.

### Examples

    data(Orthodont)
    formula(Orthodont)
    plot(Orthodont)

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