janka                 package:Rnotes                 R Documentation

_T_h_e _J_a_n_k_a _h_a_r_d_n_e_s_s _d_a_t_a

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

     Janka hardness is an important structural property of Australian
     timbers, but is difficult to measure directly. It is, however,
     directly related to the density of the timber which is relatively
     easy to measure. In an effort to develop a method of predicting
     Janka hardness from density, the Janka hardness (here considered
     the response) and the density of 36 Australian eucalypt hardwoods
     was measured.

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

     The data frame `janka' has two components: `dens' is the timber
     density for the tree and `hard' is the corresponding Janka
     hardness.

     A low-degree polynomial regression may be an appropriate model. A
     log or square-root transformation of hardness may also be useful.

_C_A_T_E_G_O_R_Y:

     Polynomial regression.  Transformations.

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

     E. J. Williams, Regression Analysis, Wiley, 1959

