hald                   package:wle                   R Documentation

_H_a_l_d _D_a_t_a

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

     Montgomery and Peck (1982) illustrated variable selection
     techniques on the Hald cement data and gave several references to
     other analysis. The response variable y is the heat evolved in a
     cement mix. The four explanatory variables are ingredients of the
     mix, i.e., x1: tricalcium aluminate, x2: tricalcium silicate, x3:
     tetracalcium alumino ferrite, x4: dicalcium silicate. An important
     feature of these data is that the variables x1 and x3 are highly
     correlated (corr(x1,x3)=-0.824), as well as the variables x2 and
     x4 (with corr(x2,x4)=-0.975). Thus we should expect any subset of
     (x1,x2,x3,x4) that includes one variable from highly correlated
     pair to do as any subset that also includes the other member.

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

     data(hald)

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

     `hald' is a matrix with 13 observations (rows) and 5 variables
     (columns), the first column is the dependent variable. `y.hald'
     and `x.hald' are also availables.

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

     Montgomery, D.C., Peck, E.A. (1982)  Introduction to linear
     regression analysis, John Wiley, New York.

