uniquecombs               package:mgcv               R Documentation

_f_i_n_d _t_h_e _u_n_i_q_u_e _r_o_w_s _i_n _a _m_a_t_r_i_x

_D_e_s_c_r_i_p_t_i_o_n:

     This routine returns a matrix containing all the unique rows of
     the matrix supplied as its argument. That is, all the duplicate
     rows are stripped out. Note that the ordering of the rows on exit
     is not the same as on entry. It also returns an index attribute
     for relating the result back  to the original matrix.

_U_s_a_g_e:

     uniquecombs(x)

_A_r_g_u_m_e_n_t_s:

       x: is an R matrix (numeric) 

_D_e_t_a_i_l_s:

     Models with more parameters than unique combinations of covariates
     are not identifiable. This routine provides a means of evaluating
     the number of unique combinations of coavariates in a model. The
     routine calls compiled C code.

_V_a_l_u_e:

     A matrix consisting of the unique rows of 'x' (in arbitrary
     order).

     The matrix has an '"index"' attribute. 'index[i]' gives the row of
     the returned  matrix that contains row i of the original matrix.

_A_u_t_h_o_r(_s):

     Simon N. Wood simon.wood@r-project.org

_S_e_e _A_l_s_o:

     'unique' can do the same thing, including for non-numeric
     matrices, but more  slowly and without returning the index.

_E_x_a_m_p_l_e_s:

     X<-matrix(c(1,2,3,1,2,3,4,5,6,1,3,2,4,5,6,1,1,1),6,3,byrow=TRUE)
     print(X)
     Xu <- uniquecombs(X);Xu
     ind <- attr(Xu,"index")
     ## find the value for row 3 of the original from Xu
     Xu[ind[3],];X[3,]

