

   BBooxx--CCooxx TTrraannssffoorrmmaattiioonnss ffoorr LLiinneeaarr MMooddeellss

        boxcox(model, lambda, plotit, interp, eps, xlab, ylab, ...)

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

      model: a formula or fitted model object.  Currently only
             `lm' and `aov' objects are handled.

     lambda: vector of values of `lambda' - default (-2, 2) in
             steps of 0.1

     plotit: logical which controls whether the result should
             be plotted.  Default to `true' if a graphics
             device is currently open.

     interp: logical which controls whether spline interpola-
             tion is used.  Default to `true' if plotting with
             `lambda' of length less than 100.

        eps: Tolerance for `lambda = 0'; defaults to 0.02

       xlab: defaults to `"lambda"'

       ylab: defaults to `"log-Likelihood"'

        ...: additional parameters to be used in the model fit-
             ting.

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

        Computes and optionally plots profile log-likelihoods
        for the parameter of the Box-Cox simple power transfor-
        mation `y^lambda'.

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

        A list of the `lambda' vector and the computed profile
        log-likelihood vector, invisibly if the result is plot-
        ted.

   SSiiddee EEffffeeccttss::

        If `plotit = T' plots loglik vs `lambda' and indicates
        a 95% confidence interval about the maximum observed
        value of `lambda'. If `interp = T', spline interpola-
        tion is used to give a smoother plot.

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

        data(trees)
        boxcox(volume ~ log(height) + log(diam), data = trees,
               lambda = seq(-0.25, 0.25, length = 10))

