

   CCoonnttiinnuuoouuss AARR((11)) CCoorrrreellaattiioonn SSttrruuccttuurree

        corCAR1(value, form)

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

      value: the correlation between two observations one unit
             of time apart. Must be between 0 and 1. Defaults
             to 0.2.

       form: a one sided formula of the form `~ t', or code{~ t
             | g}, specifying a time covariate `t' and,
             optionally, a grouping factor `g'. Covariates for
             this correlation structure need not be integer
             valued.  When a grouping factor is present in
             `form', the correlation structure is assumed to
             apply only to observations within the same group-
             ing level; observations with different grouping
             levels are assumed to be uncorrelated. Defaults to
             `~ 1', which corresponds to using the order of the
             observations in the data as a covariate, and no
             groups.

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

        This function is a constructor for the `corCAR1' class,
        representing an autocorrelation structure of order 1,
        with a continuous time covariate. Objects created using
        this constructor need to be later initialized using the
        appropriate `initialize' method.

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

        an object of class `corCAR1', representing an autocor-
        relation structure of order 1, with a continuous time
        covariate.

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

        Jose Pinheiro and Douglas Bates

   RReeffeerreenncceess::

        Box, G.E.P., Jenkins, G.M., and Reinsel G.C. (1994)
        "Time Series Analysis: Forecasting and Control", 3rd
        Edition, Holden-Day.

   SSeeee AAllssoo::

        `initialize.corStruct'

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

        library(lme)
        ## covariate is Time and grouping factor is Mare
        cs1 <- corCAR1(0.2, form = ~ Time | Mare)

