Orthodont                package: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:

     formula(Orthodont)
     plot(Orthodont)

