AsIs                  package:base                  R Documentation

_I_n_h_i_b_i_t _I_n_t_e_r_p_r_e_t_a_t_i_o_n/_C_o_n_v_e_r_s_i_o_n _o_f _O_b_j_e_c_t_s

_D_e_s_c_r_i_p_t_i_o_n:

     Change the class of an object to indicate that it should be
     treated 'as is'.

_U_s_a_g_e:

     I(x)

_A_r_g_u_m_e_n_t_s:

       x: an object

_D_e_t_a_i_l_s:

     Function 'I' has two main uses.

        *  In function 'data.frame'.  Protecting an object by enclosing
           it in 'I()' in a call to 'data.frame' inhibits the
           conversion of character vectors to factors and the dropping
           of names, and ensures that matrices are inserted as single
           columns. 'I' can also be used to protect objects which are
           to be added to a data frame, or converted to a data frame
           _via_ 'as.data.frame'.

           It achieves this by prepending the class '"AsIs"' to the
           object's classes.  Class '"AsIs"' has a few of its own
           methods, including for '[', 'as.data.frame', 'print' and
           'format'.

        *  In function 'formula'.  There it is used to inhibit the
           interpretation of  operators such as '"+"', '"-"', '"*"' and
           '"^"' as formula operators, so they are used as arithmetical
           operators.  This is interpreted as a symbol by
           'terms.formula'.

_V_a_l_u_e:

     A copy of the object with class '"AsIs"' prepended to the
     class(es).

_R_e_f_e_r_e_n_c_e_s:

     Chambers, J. M. (1992) _Linear models._ Chapter 4 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', 'formula'

