Grass                package:candisc                R Documentation

_Y_i_e_l_d_s _f_r_o_m _N_i_t_r_o_g_e_n _n_u_t_r_i_t_i_o_n _o_f _g_r_a_s_s _s_p_e_c_i_e_s

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

     The data frame 'Grass' gives the yield (10 * log10 dry-weight (g))
     of eight grass Species in five replicates (Block) grown in sand
     culture at five levels of nitrogen.

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

     data(Grass)

_F_o_r_m_a_t:

     A data frame with 40 observations on the following 7 variables.

     '_S_p_e_c_i_e_s' a factor with levels  'B.media' 'D.glomerata' 'F.ovina'
          'F.rubra' 'H.pubesens'  'K.cristata' 'L.perenne'
          'P.bertolonii'

     '_B_l_o_c_k' a factor with levels '1' '2' '3' '4' '5'

     '_N_1' species yield at 1 ppm Nitrogen

     '_N_9' species yield at 9 ppm Nitrogen

     '_N_2_7' species yield at 27 ppm Nitrogen

     '_N_8_1' species yield at 81 ppm Nitrogen

     '_N_2_4_3' species yield at 243 ppm Nitrogen

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

     Nitrogen (NaNO3) levels were chosen to vary from what was expected
     to be from critically low to almost toxic.  The amount of Nitrogen
     can be considered on a log3 scale, with levels 0, 2, 3, 4, 5. 
     Gittins (1985, Ch. 11) treats these as equally spaced for the
     purpose of testing polynomial trends in Nitrogen level.

     The data are also not truly multivariate, but rather a split-plot
     experimental design. For the purpose of exposition, he regards
     Species as the experimental unit, so that correlations among the
     responses refer to a composite representative of a species rather
     than to an individual exemplar.

_S_o_u_r_c_e:

     Gittins, R. (1985), Canonical Analysis: A Review with Applications
     in Ecology, Berlin: Springer-Verlag, Table A-5.

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

     str(Grass)
     grass.mod <- lm(cbind(N1,N9,N27,N81,N243) ~ Block + Species, data=Grass)

