pitpropC                 package:sca                 R Documentation

_P_i_t_p_r_o_p_s _S_t_r_e_n_g_t_h _C_o_r_r_e_l_a_t_i_o_n _D_a_t_a

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

     This correlation matrix was published in Jeffers (1967) and was
     calculated from 180 observations. The 13 variables were used as
     explanatory variables in a regression problem which arised from a
     study on the strength of pitprops cut from home-grown timber.

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

     data(pitpropC)

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

     Its a correlation matrix of 13 variables which have the following
     meaning:

        [,1]  TOPDIAM  Top diameter of the prop in inches
        [,2]  LENGTH   Length of the prop in inches
        [,3]  MOIST    Moisture content of the prop, expressed as a percentage of the dry weight
        [,4]  TESTSG   Specific gravity of the timber at the time of the test
        [,5]  OVENSG   Oven-dry specific gravity of the timber
        [,6]  RINGTOP  Number of annual rings at the top of the prop
        [,7]  RINGBUT  Number of annual rings at the base of the prop
        [,8]  BOWMAX   Maximum bow in inches
        [,9]  BOWDIST  Distance of the point of maximum bow from the top of the prop in inches
       [,10]  WHORLS   Number of knot whorls
       [,11]  CLEAR    Length of clear prop from the top of the prop in inches
       [,12]  KNOTS    Average number of knots per whorl
       [,13]  DIAKNOT  Average diameter of the knots in inches

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

     Jeffers (1967) replaced these 13 variables by their first six
     principal components.  As noted by Vines (2000), this is an
     example where simple structure has proven difficult to detect in
     the past.

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

     Jeffers, J.N.R. (1967) Two case studies in the application of
     principal components analysis. _Appl. Statist._ *16*, 225-236.

     Vines, S.K. (2000) Simple principal components. _Appl. Statist._
     *49*, 441-451.

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

     data(pitpropC)
     symnum(pitpropC)

