VarCorr                 package:nlme                 R Documentation

Extract variance and correlation components

Description:

     This function calculates the estimated variances, standard
     deviations, and correlations between the random-effects terms in a
     linear mixed-effects model, of class 'lme', or a nonlinear
     mixed-effects model, of class 'nlme'. The within-group error
     variance and standard deviation are also calculated.

Usage:

     VarCorr(x, sigma, rdig)

Arguments:

       x: a fitted model object, usually an object inheriting from
          class 'lme'.  

   sigma: an optional numeric value used as a multiplier for the
          standard deviations. Default is '1'. 

    rdig: an optional integer value specifying the number of digits
          used to represent correlation estimates. Default is '3'. 

Value:

     a matrix with the estimated variances, standard deviations, and
     correlations for the random effects. The first two columns, named
     'Variance' and 'StdDev', give, respectively, the variance and the
     standard deviations. If there are correlation components in the
     random effects model, the third column, named 'Corr', and the
     remaining unnamed columns give the estimated correlations among
     random effects within the same level of grouping. The within-group
     error variance and standard deviation are included as the last row
     in the matrix.

Author(s):

     Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates
     bates@stat.wisc.edu

References:

     Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S
     and S-PLUS", Springer, esp. pp. 100, 461.

See Also:

     'lme', 'nlme'

Examples:

     fm1 <- lme(distance ~ age, data = Orthodont, random = ~age)
     VarCorr(fm1)

