contrMat              package:multcomp              R Documentation

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

_D_e_s_c_r_i_p_t_i_o_n:

     Computes contrast matrices for several multiple comparision
     procedures.

_U_s_a_g_e:

     contrMat(n, type=c("Dunnett", "Tukey", "Sequen", "AVE", 
                        "Changepoint", "Williams", "Marcus", 
                        "McDermott", "Tetrade"), nlevel = NULL, base = 1)
     contr.Dunnett(n, base = 1, contrasts=TRUE)

_A_r_g_u_m_e_n_t_s:

       n: a (possibly named) vector of sample sizes for each group or a
          vector of factor levels. 

    type: type of contrast. 

  nlevel: number of levels of two factors (for 'type="Tetrade"' only).

contrasts: a logical indicating whether contrasts should be computed.

    base: an integer specifying which group is considered the baseline
          group for Dunnett contrasts. Ignored if 'contrasts' is
          'FALSE'.

_D_e_t_a_i_l_s:

     Computes the requested matrix of contrasts.

_V_a_l_u_e:

     The matrix of contrasts with appropriate rownames is returned.

_A_u_t_h_o_r(_s):

     Frank Bretz <bretz@ifgb.uni-hannover.de> and  
      Torsten Hothorn <Torsten.Hothorn@rzmail.uni-erlangen.de>

_R_e_f_e_r_e_n_c_e_s:

     Frank Bretz, Alan Genz and Ludwig A. Hothorn (2001), On the
     numerical  availability of multiple comparison procedures.
     _Biometrical Journal_, *43*(5), 645-656.

_E_x_a_m_p_l_e_s:

      n <- c(10,20,30,40)
      a <- 2
      b <- 3
      names(n) <- paste("group", 1:4, sep="")
      contrMat(n)    # Dunnett is default
      contrMat(n, base=2)    # use second level as baseline
      contr.Dunnett(names(n))  # it Moore-Penrose Inverse
      contrMat(n, type="Tukey")
      contrMat(n, type="Sequen")
      contrMat(n, type="AVE")
      contrMat(n, type="Changepoint")
      contrMat(n, type="Williams")
      contrMat(n, type="Marcus")
      contrMat(n, type="McDermott")
      contrMat(n, type="Tetrade", nlevel=c(a,b))

