

   CCoonnttrraasstt MMaattrriicceess

        contr.helmert(n, contrasts=TRUE)
        contr.poly(n, contrasts=TRUE)
        contr.sum(n, contrasts=TRUE)
        contr.treatment(n, contrasts=TRUE)

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

        A matrix with `n' rows and `k' columns, with `k=n-1' if
        `contrasts' is `TRUE' and `k=n' if `contrasts' is
        `FALSE'.

        These functions are used for creating contrast matrices
        for use in fitting analysis of variance and regression
        models.  The columns of the resulting matrices contain
        contrasts which can be used for coding a factor with
        `n' levels.  The returned value contains the computed
        contrasts.  If the argument `contrasts' is `FALSE' then
        an additional column of ones is prepended to the
        matrix.

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

        `contrasts', `glm', `lm'.

