row.names                package:base                R Documentation

_G_e_t _a_n_d _S_e_t _R_o_w _N_a_m_e_s _f_o_r _D_a_t_a _F_r_a_m_e_s

_D_e_s_c_r_i_p_t_i_o_n:

     All data frames have a row names attribute, a character vector of
     length the number of rows with no duplicates nor missing values.

     For convenience, these are generic functions for which users can
     write other methods, and there are default methods for arrays. 
     The description here is for the 'data.frame' method.

_U_s_a_g_e:

     row.names(x)
     row.names(x) <- value

_A_r_g_u_m_e_n_t_s:

       x: object of class '"data.frame"', or any other class for which
          a method has been defined.

   value: an object to be coerced to character unless an integer
          vector.  It should have (after coercion) the same length as
          the number of rows of 'x' with no duplicated nor missing
          values. 'NULL' is also allowed: see Details.

_D_e_t_a_i_l_s:

     A data frame has (by definition) a vector of _row names_ which has
     length the number of rows in the data frame, and contains neither
     missing nor duplicated values.  Where a row names sequence has
     been added by the software to meet this requirement, they are
     regarded as 'automatic'.

     Prior to R 2.4.0, row names were character.  As from R 2.4.0, they
     are allowed to be integer or character, but for backwards
     compatibility 'row.names' will always return a character vector.
     (Use 'attr(x, "row.names")' if you need an integer value.)

     Using 'NULL' for the value resets the row names to
     'seq_len(nrow(x))', regarded as 'automatic'.

_V_a_l_u_e:

     'row.names' returns a character vector.

     'row.names<-' returns a data frame with the row names changed.

_N_o_t_e:

     'row.names' is similar to 'rownames' for arrays, and it has a
     method that calls 'rownames' for an array argument.

     Row names of the form '1:n' for 'n > 2' are stored internally in a
     compact form, which might be seen from C code or by deparsing but
     never via 'row.names' or 'attr(x, "row.names")'.  Additionally,
     some names of this sort are marked as 'automatic' and handled
     differently by 'as.matrix' and 'data.matrix' (and potentially
     other functions).  (All zero-row data frames are regarded as
     having automatic row.names.)

_R_e_f_e_r_e_n_c_e_s:

     Chambers, J. M. (1992) _Data for models._ Chapter 3 of
     _Statistical Models in S_ eds J. M. Chambers and T. J. Hastie,
     Wadsworth & Brooks/Cole.

_S_e_e _A_l_s_o:

     'data.frame', 'rownames', 'names'.

     '.row_names_info' for the internal representations.

