dgTMatrix-class            package:Matrix            R Documentation

_S_p_a_r_s_e _m_a_t_r_i_c_e_s _i_n _t_r_i_p_l_e_t _f_o_r_m

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

     The '"dgTMatrix"' class is the class of sparse matrices stored as
     (possibly redundant) triplets.  The internal representation is not
     at all unique, contrary to the one for class 'dgCMatrix'.

_O_b_j_e_c_t_s _f_r_o_m _t_h_e _C_l_a_s_s:

     Objects can be created by calls of the form 'new("dgTMatrix",
     ...)', but more typically via 'as(*, "dgTMatrix")'.

_S_l_o_t_s:


     '_i': Object of class '"integer"' - the row indices of non-zero
          entries _in 0-base_, i.e., must be in '0:(nrow(.)-1)'.

     '_j': Object of class '"integer"' - the column indices of non-zero
          entries.  Must be the same length as slot 'i' and _0-based_
          as well, i.e., in '0:(ncol(.)-1)'.

     '_x': Object of class '"numeric"' - the (non-zero) entry at
          position '(i,j)'.  Must be the same length as slot 'i'. If an
          index pair occurs more than once the corresponding values of
          slot 'x' are added to form the element of the matrix.

     '_D_i_m': Object of class '"integer"' of length 2 - the dimensions of
          the matrix.

_M_e_t_h_o_d_s:


     + 'signature(e1 = "dgTMatrix", e2 = "dgTMatrix")'

     _c_o_e_r_c_e 'signature(from = "dgTMatrix", to = "dgCMatrix")'

     _c_o_e_r_c_e 'signature(from = "dgTMatrix", to = "dgeMatrix")'

     _c_o_e_r_c_e 'signature(from = "dgTMatrix", to = "matrix")', and
          typically coercion methods for more specific signatures, we
          are not mentioning here.

          Note that these are not guaranteed to continue to exist, but
          rather you should use calls like 'as(x, "CsparseMatrix")',
          'as(x, "generalMatrix")', 'as(x, "dMatrix")', i.e. coercion
          to higher level virtual classes.

     _c_o_e_r_c_e 'signature(from = "matrix", to = "dgTMatrix")', (direct
          coercion from tradition matrix).

     _c_r_o_s_s_p_r_o_d 'signature(x = "dgTMatrix", y = "missing")' returns
          't(x) %*% x' as an 'dsCMatrix' object.

     _c_r_o_s_s_p_r_o_d 'signature(x = "dgTMatrix", y = "matrix")': ... 

     _c_r_o_s_s_p_r_o_d 'signature(x = "dgTMatrix", y = "numeric")': ... 

     _i_m_a_g_e 'signature(x = "dgTMatrix")': plots an image of 'x' using
          the 'levelplot' function

     _t 'signature(x = "dgTMatrix")': returns the transpose of 'x'

_N_o_t_e:

     Triplet matrices are a convenient form in which to construct
     sparse matrices after which they can be coerced to 'dgCMatrix'
     objects.

_S_e_e _A_l_s_o:

     Class 'dgCMatrix' or the superclasses 'dsparseMatrix' and
     'TsparseMatrix';

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

     m <- Matrix(0+1:28, nrow = 4)
     m[-3,c(2,4:5,7)] <- m[ 3, 1:4] <- m[1:3, 6] <- 0
     (mT <- as(m, "dgTMatrix"))
     str(mT)
     mT[1,]
     mT[4, drop = FALSE]
     stopifnot(identical(mT[lower.tri(mT)],
                         m [lower.tri(m) ]))
     mT[lower.tri(mT,diag=TRUE)] <- 0
     mT

