

   EExxttrraacctt vvaarriiaannccee aanndd ccoorrrreellaattiioonn ccoommppoonneennttss

        VarCorr(object, sigma, rdig)

   AArrgguummeennttss::

     object: a fitted model object, usually an object inherit-
             ing 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'.

   DDeessccrriippttiioonn::

        This function calculates the estimated variances, stan-
        dard 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.

   VVaalluuee::

        a matrix with the estimated variances, standard devia-
        tions, 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 correla-
        tions 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.

   AAuutthhoorr((ss))::

        Jose Pinheiro and Douglas Bates

   EExxaammpplleess::

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

