Pixel                  package:nlme                  R Documentation

_X-_r_a_y _p_i_x_e_l _i_n_t_e_n_s_i_t_i_e_s _o_v_e_r _t_i_m_e

_D_e_s_c_r_i_p_t_i_o_n:

     The 'Pixel' data frame has 102 rows and 4 columns of data on the
     pixel intensities of CT scans of dogs over time

_F_o_r_m_a_t:

     This data frame contains the following columns:

     _D_o_g a factor with levels '1' to '10' designating the dog on which
          the scan was made

     _S_i_d_e a factor with levels 'L' and 'R' designating the side of the
          dog being scanned

     _d_a_y a numeric vector giving the day post injection of the contrast
          on which the scan was made

     _p_i_x_e_l a numeric vector of pixel intensities


_S_o_u_r_c_e:

     Pinheiro, J. C. and Bates, D. M. (2000) _Mixed-effects Models in S
     and S-PLUS_, Springer.

_E_x_a_m_p_l_e_s:

     fm1 <- lme(pixel ~ day + I(day^2), data = Pixel,
                random = list(Dog = ~ day, Side = ~ 1))
     summary(fm1)
     VarCorr(fm1)