

_C_o_n_t_r_a_s_t _M_a_t_r_i_c_e_s

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

_V_a_l_u_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.

     Note that as from version 0.62.2 `contr.poly' returns
     contrasts based on orthogonal (rather than raw) polyno-
     mials.

_S_e_e _A_l_s_o:

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

